docs: def named_field(key, regex, vim=False):
      """
      Creates a named regex group that can be referend via a backref.
      If key is None the backref is referenced by number.
  
      References:
          https://docs.python.org/2/library/re.html#regular-expression-syntax
      """
      if key is None:
          #return regex
          return r'(%s)' % (regex,)
      if vim:
          return r'\(%s\)' % (regex)
      else:
          return r'(?P<%s>%s)' % (key, regex)