Update black (#4814)

20 files changed, 37 insertions, 37 deletions

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index f317fc27..c02635bd 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -2,7 +2,7 @@
 # pre-commit install
 
 repos:
--   repo: https://github.com/ambv/black
-    rev: 20.8b1
+-   repo: https://github.com/psf/black
+    rev: 21.5b1
     hooks:
     - id: black
diff --git a/networkx/algorithms/centrality/tests/test_current_flow_betweenness_centrality.py b/networkx/algorithms/centrality/tests/test_current_flow_betweenness_centrality.py
index 166df59a..69b06cb9 100644
--- a/networkx/algorithms/centrality/tests/test_current_flow_betweenness_centrality.py
+++ b/networkx/algorithms/centrality/tests/test_current_flow_betweenness_centrality.py
@@ -59,7 +59,7 @@ class TestFlowBetweennessCentrality:
             assert almost_equal(b[n], b_answer[n])
 
     def test_star(self):
-        """Betweenness centrality: star """
+        """Betweenness centrality: star"""
         G = nx.Graph()
         nx.add_star(G, ["a", "b", "c", "d"])
         b = nx.current_flow_betweenness_centrality(G, normalized=True)
diff --git a/networkx/algorithms/centrality/tests/test_current_flow_betweenness_centrality_subset.py b/networkx/algorithms/centrality/tests/test_current_flow_betweenness_centrality_subset.py
index 15b0773b..47e41b3f 100644
--- a/networkx/algorithms/centrality/tests/test_current_flow_betweenness_centrality_subset.py
+++ b/networkx/algorithms/centrality/tests/test_current_flow_betweenness_centrality_subset.py
@@ -76,7 +76,7 @@ class TestFlowBetweennessCentrality:
             assert almost_equal(b[n], b_answer[n])
 
     def test_star(self):
-        """Betweenness centrality: star """
+        """Betweenness centrality: star"""
         G = nx.Graph()
         nx.add_star(G, ["a", "b", "c", "d"])
         b = nx.current_flow_betweenness_centrality_subset(
diff --git a/networkx/algorithms/centrality/tests/test_current_flow_closeness.py b/networkx/algorithms/centrality/tests/test_current_flow_closeness.py
index 338c9613..c2fa4ec0 100644
--- a/networkx/algorithms/centrality/tests/test_current_flow_closeness.py
+++ b/networkx/algorithms/centrality/tests/test_current_flow_closeness.py
@@ -25,7 +25,7 @@ class TestFlowClosenessCentrality:
             assert almost_equal(b[n], b_answer[n])
 
     def test_star(self):
-        """Closeness centrality: star """
+        """Closeness centrality: star"""
         G = nx.Graph()
         nx.add_star(G, ["a", "b", "c", "d"])
         b = nx.current_flow_closeness_centrality(G)
diff --git a/networkx/algorithms/chordal.py b/networkx/algorithms/chordal.py
index 19447486..7c7177af 100644
--- a/networkx/algorithms/chordal.py
+++ b/networkx/algorithms/chordal.py
@@ -274,7 +274,7 @@ def _is_complete_graph(G):
 
 
 def _find_missing_edge(G):
-    """ Given a non-complete graph G, returns a missing edge."""
+    """Given a non-complete graph G, returns a missing edge."""
     nodes = set(G)
     for u in G:
         missing = nodes - set(list(G[u].keys()) + [u])
diff --git a/networkx/algorithms/connectivity/edge_augmentation.py b/networkx/algorithms/connectivity/edge_augmentation.py
index ff2c44c9..b78cec11 100644
--- a/networkx/algorithms/connectivity/edge_augmentation.py
+++ b/networkx/algorithms/connectivity/edge_augmentation.py
@@ -334,7 +334,7 @@ def partial_k_edge_augmentation(G, k, avail, weight=None):
     """
 
     def _edges_between_disjoint(H, only1, only2):
-        """ finds edges between disjoint nodes """
+        """finds edges between disjoint nodes"""
         only1_adj = {u: set(H.adj[u]) for u in only1}
         for u, neighbs in only1_adj.items():
             # Find the neighbors of u in only1 that are also in only2
diff --git a/networkx/algorithms/connectivity/tests/test_edge_augmentation.py b/networkx/algorithms/connectivity/tests/test_edge_augmentation.py
index dfef3635..600ab13e 100644
--- a/networkx/algorithms/connectivity/tests/test_edge_augmentation.py
+++ b/networkx/algorithms/connectivity/tests/test_edge_augmentation.py
@@ -249,7 +249,7 @@ def test_gnp_augmentation():
 
 
 def _assert_solution_properties(G, aug_edges, avail_dict=None):
-    """ Checks that aug_edges are consistently formatted """
+    """Checks that aug_edges are consistently formatted"""
     if avail_dict is not None:
         assert all(
             e in avail_dict for e in aug_edges
@@ -392,7 +392,7 @@ def _augment_and_check(
 
 
 def _check_augmentations(G, avail=None, max_k=None, weight=None, verbose=False):
-    """ Helper to check weighted/unweighted cases with multiple values of k """
+    """Helper to check weighted/unweighted cases with multiple values of k"""
     # Using all available edges, find the maximum edge-connectivity
     try:
         orig_k = nx.edge_connectivity(G)
diff --git a/networkx/algorithms/connectivity/tests/test_edge_kcomponents.py b/networkx/algorithms/connectivity/tests/test_edge_kcomponents.py
index f62807a1..08aa3232 100644
--- a/networkx/algorithms/connectivity/tests/test_edge_kcomponents.py
+++ b/networkx/algorithms/connectivity/tests/test_edge_kcomponents.py
@@ -12,7 +12,7 @@ from networkx.algorithms.connectivity.edge_kcomponents import general_k_edge_sub
 
 
 def fset(list_of_sets):
-    """ allows == to be used for list of sets """
+    """allows == to be used for list of sets"""
     return set(map(frozenset, list_of_sets))
 
 
diff --git a/networkx/algorithms/isomorphism/vf2userfunc.py b/networkx/algorithms/isomorphism/vf2userfunc.py
index 6cd7bde1..349129ee 100644
--- a/networkx/algorithms/isomorphism/vf2userfunc.py
+++ b/networkx/algorithms/isomorphism/vf2userfunc.py
@@ -186,12 +186,12 @@ class DiGraphMatcher(vf2.DiGraphMatcher):
 
 
 class MultiGraphMatcher(GraphMatcher):
-    """VF2 isomorphism checker for undirected multigraphs. """
+    """VF2 isomorphism checker for undirected multigraphs."""
 
     pass
 
 
 class MultiDiGraphMatcher(DiGraphMatcher):
-    """VF2 isomorphism checker for directed multigraphs. """
+    """VF2 isomorphism checker for directed multigraphs."""
 
     pass
diff --git a/networkx/algorithms/tests/test_simple_paths.py b/networkx/algorithms/tests/test_simple_paths.py
index 57e9d82f..aaf9a051 100644
--- a/networkx/algorithms/tests/test_simple_paths.py
+++ b/networkx/algorithms/tests/test_simple_paths.py
@@ -148,7 +148,7 @@ def test_all_simple_paths_cutoff():
 
 
 def test_all_simple_paths_on_non_trivial_graph():
-    """ you may need to draw this graph to make sure it is reasonable """
+    """you may need to draw this graph to make sure it is reasonable"""
     G = nx.path_graph(5, create_using=nx.DiGraph())
     G.add_edges_from([(0, 5), (1, 5), (1, 3), (5, 4), (4, 2), (4, 3)])
     paths = nx.all_simple_paths(G, 1, [2, 3])
@@ -334,7 +334,7 @@ def test_all_simple_edge_paths_cutoff():
 
 
 def test_all_simple_edge_paths_on_non_trivial_graph():
-    """ you may need to draw this graph to make sure it is reasonable """
+    """you may need to draw this graph to make sure it is reasonable"""
     G = nx.path_graph(5, create_using=nx.DiGraph())
     G.add_edges_from([(0, 5), (1, 5), (1, 3), (5, 4), (4, 2), (4, 3)])
     paths = nx.all_simple_edge_paths(G, 1, [2, 3])
diff --git a/networkx/classes/function.py b/networkx/classes/function.py
index 1d2f2866..4f44b12e 100644
--- a/networkx/classes/function.py
+++ b/networkx/classes/function.py
@@ -76,7 +76,7 @@ def degree(G, nbunch=None, weight=None):
 
 
 def neighbors(G, n):
-    """Returns a list of nodes connected to node n. """
+    """Returns a list of nodes connected to node n."""
     return G.neighbors(n)
 
 
@@ -86,7 +86,7 @@ def number_of_nodes(G):
 
 
 def number_of_edges(G):
-    """Returns the number of edges in the graph. """
+    """Returns the number of edges in the graph."""
     return G.number_of_edges()
 
 
@@ -149,7 +149,7 @@ def degree_histogram(G):
 
 
 def is_directed(G):
-    """ Return True if graph is directed."""
+    """Return True if graph is directed."""
     return G.is_directed()
 
 
diff --git a/networkx/classes/tests/test_graph.py b/networkx/classes/tests/test_graph.py
index 41de0ce9..476f5e14 100644
--- a/networkx/classes/tests/test_graph.py
+++ b/networkx/classes/tests/test_graph.py
@@ -13,7 +13,7 @@ import pytest
 
 
 class BaseGraphTester:
-    """ Tests for data-structure independent graph class features."""
+    """Tests for data-structure independent graph class features."""
 
     def test_contains(self):
         G = self.K3
@@ -160,7 +160,7 @@ class BaseGraphTester:
 
 
 class BaseAttrGraphTester(BaseGraphTester):
-    """ Tests of graph class attribute features."""
+    """Tests of graph class attribute features."""
 
     def test_weighted_degree(self):
         G = self.Graph()
diff --git a/networkx/generators/line.py b/networkx/generators/line.py
index 49132eff..55954c74 100644
--- a/networkx/generators/line.py
+++ b/networkx/generators/line.py
@@ -324,7 +324,7 @@ def inverse_line_graph(G):
 
 
 def _triangles(G, e):
-    """ Return list of all triangles containing edge e"""
+    """Return list of all triangles containing edge e"""
     u, v = e
     if u not in G:
         raise nx.NetworkXError(f"Vertex {u} not in graph")
diff --git a/networkx/generators/small.py b/networkx/generators/small.py
index bcfb741b..a5449c78 100644
--- a/networkx/generators/small.py
+++ b/networkx/generators/small.py
@@ -181,7 +181,7 @@ def LCF_graph(n, shift_list, repeats, create_using=None):
 
 
 def bull_graph(create_using=None):
-    """Returns the Bull graph. """
+    """Returns the Bull graph."""
     description = [
         "adjacencylist",
         "Bull Graph",
@@ -239,14 +239,14 @@ def cubical_graph(create_using=None):
 
 
 def desargues_graph(create_using=None):
-    """ Return the Desargues graph."""
+    """Return the Desargues graph."""
     G = LCF_graph(20, [5, -5, 9, -9], 5, create_using)
     G.name = "Desargues Graph"
     return G
 
 
 def diamond_graph(create_using=None):
-    """Returns the Diamond graph. """
+    """Returns the Diamond graph."""
     description = [
         "adjacencylist",
         "Diamond Graph",
@@ -258,7 +258,7 @@ def diamond_graph(create_using=None):
 
 
 def dodecahedral_graph(create_using=None):
-    """ Return the Platonic Dodecahedral graph. """
+    """Return the Platonic Dodecahedral graph."""
     G = LCF_graph(20, [10, 7, 4, -4, -7, 10, -4, 7, -7, 4], 2, create_using)
     G.name = "Dodecahedral Graph"
     return G
@@ -293,7 +293,7 @@ def frucht_graph(create_using=None):
 
 
 def heawood_graph(create_using=None):
-    """ Return the Heawood graph, a (3,6) cage. """
+    """Return the Heawood graph, a (3,6) cage."""
     G = LCF_graph(14, [5, -5], 7, create_using)
     G.name = "Heawood Graph"
     return G
@@ -416,7 +416,7 @@ def octahedral_graph(create_using=None):
 
 
 def pappus_graph():
-    """ Return the Pappus graph."""
+    """Return the Pappus graph."""
     G = LCF_graph(18, [5, 7, -7, 7, -7, -5], 3)
     G.name = "Pappus Graph"
     return G
@@ -464,7 +464,7 @@ def sedgewick_maze_graph(create_using=None):
 
 
 def tetrahedral_graph(create_using=None):
-    """ Return the 3-regular Platonic Tetrahedral graph."""
+    """Return the 3-regular Platonic Tetrahedral graph."""
     G = complete_graph(4, create_using)
     G.name = "Platonic Tetrahedral graph"
     return G
diff --git a/networkx/generators/tests/test_interval_graph.py b/networkx/generators/tests/test_interval_graph.py
index ec442b81..0c7b4292 100644
--- a/networkx/generators/tests/test_interval_graph.py
+++ b/networkx/generators/tests/test_interval_graph.py
@@ -13,11 +13,11 @@ class TestIntervalGraph:
     """Unit tests for :func:`networkx.generators.interval_graph.interval_graph`"""
 
     def test_empty(self):
-        """ Tests for trivial case of empty input"""
+        """Tests for trivial case of empty input"""
         assert len(interval_graph([])) == 0
 
     def test_interval_graph_check_invalid(self):
-        """ Tests for conditions that raise Exceptions """
+        """Tests for conditions that raise Exceptions"""
 
         invalids_having_none = [None, (1, 2)]
         with pytest.raises(TypeError):
@@ -92,7 +92,7 @@ class TestIntervalGraph:
         assert_edges_equal(expected_graph, actual_g)
 
     def test_interval_graph_4(self):
-        """ test all possible overlaps """
+        """test all possible overlaps"""
         intervals = [
             (0, 2),
             (-2, -1),
@@ -129,7 +129,7 @@ class TestIntervalGraph:
         assert set(actual_nbrs) == expected_nbrs
 
     def test_interval_graph_5(self):
-        """ this test is to see that an interval supports infinite number"""
+        """this test is to see that an interval supports infinite number"""
         intervals = {(-math.inf, 0), (-1, -1), (0.5, 0.5), (1, 1), (1, math.inf)}
 
         expected_graph = nx.Graph()
diff --git a/networkx/generators/tests/test_joint_degree_seq.py b/networkx/generators/tests/test_joint_degree_seq.py
index dd898d31..346ebefc 100644
--- a/networkx/generators/tests/test_joint_degree_seq.py
+++ b/networkx/generators/tests/test_joint_degree_seq.py
@@ -10,7 +10,7 @@ from networkx.generators.joint_degree_seq import (
 
 
 def test_is_valid_joint_degree():
-    """ Tests for conditions that invalidate a joint degree dict """
+    """Tests for conditions that invalidate a joint degree dict"""
 
     # valid joint degree that satisfies all five conditions
     joint_degrees = {
diff --git a/networkx/readwrite/gml.py b/networkx/readwrite/gml.py
index 03c7139b..bc3ef710 100644
--- a/networkx/readwrite/gml.py
+++ b/networkx/readwrite/gml.py
@@ -260,7 +260,7 @@ def parse_gml(lines, label="label", destringizer=None):
 
 
 class Pattern(Enum):
-    """ encodes the index of each token-matching pattern in `tokenize`. """
+    """encodes the index of each token-matching pattern in `tokenize`."""
 
     KEYS = 0
     REALS = 1
diff --git a/networkx/readwrite/graphml.py b/networkx/readwrite/graphml.py
index cd8fcbc1..1ecaebdd 100644
--- a/networkx/readwrite/graphml.py
+++ b/networkx/readwrite/graphml.py
@@ -588,7 +588,7 @@ class GraphMLWriter(GraphML):
         self.xml.append(graph_element)
 
     def add_graphs(self, graph_list):
-        """ Add many graphs to this GraphML document. """
+        """Add many graphs to this GraphML document."""
         for G in graph_list:
             self.add_graph_element(G)
 
diff --git a/networkx/utils/misc.py b/networkx/utils/misc.py
index bd58a4ed..2df5f48b 100644
--- a/networkx/utils/misc.py
+++ b/networkx/utils/misc.py
@@ -96,7 +96,7 @@ def empty_generator():
 
 
 def flatten(obj, result=None):
-    """ Return flattened version of (possibly nested) iterable object. """
+    """Return flattened version of (possibly nested) iterable object."""
     if not isinstance(obj, (Iterable, Sized)) or isinstance(obj, str):
         return obj
     if result is None:
diff --git a/requirements/developer.txt b/requirements/developer.txt
index 2cde2c06..63f5dff3 100644
--- a/requirements/developer.txt
+++ b/requirements/developer.txt
@@ -1,2 +1,2 @@
-black==20.8b1
-pre-commit==2.9.3
+black==21.5b1
+pre-commit~=2.12