code: def unpack(self, format_text):
          
          data = _unpack_from(format_text, self.data, self.offset)
          self.offset += _calcsize(format_text)
          return data
docs: Unpack bytes using struct modules format
  
          :param format_text: struct's module format
          :type  format_text: :class:`str`
          :return data: result from :func:`struct.unpack_from`
          :rtype: :class:`tuple`