---input---
**no bold__

__no bold**

*no bold*

_no bold_

---tokens---
'**no'        Text
' '           Text
'bold__'      Text
'\n'          Text

'\n'          Text

'__no'        Text
' '           Text
'bold**'      Text
'\n'          Text

'\n'          Text

'*no bold*'   Generic.Emph
'\n'          Text

'\n'          Text

'_no bold_'   Generic.Emph
'\n'          Text