code: def _get_regex(data, position, dummy0, dummy1):
      
      pattern, position = _get_c_string(data, position)
      bson_flags, position = _get_c_string(data, position)
      bson_re = Regex(pattern, bson_flags)
      return bson_re, position
docs: Decode a BSON regex to bson.regex.Regex or a python pattern object.