docs: def _get_string(data, position, obj_end, dummy):
      """Decode a BSON string to python unicode string."""
      length = _UNPACK_INT(data[position:position + 4])[0]
      position += 4
      if length < 1 or obj_end - position < length:
          raise InvalidBSON("invalid string length")
      end = position + length - 1
      if data[end:end + 1] != b"\x00":
          raise InvalidBSON("invalid end of string")
      return _utf_8_decode(data[position:end], None, True)[0], end + 1