.. change::
    :tags: change, engine
    :tickets: 7122

    Some small API changes regarding engines and dialects:

    * The :meth:`.Dialect.set_isolation_level`, :meth:`.Dialect.get_isolation_level`,
      :meth:
      dialect methods will always be passed the raw DBAPI connection

    * The :class:`.Connection` and :class:`.Engine` classes no longer share a base
      ``Connectable`` superclass, which has been removed.

    * Added a new interface class :class:`.PoolProxiedConnection` - this is the
      public facing interface for the familiar :class:`._ConnectionFairy`
      class which is nonetheless a private class.
