docs: def scp_data_length(self):
          """The maximum SCP data field length supported by the machine
          (bytes).
          """
          # If not known, query the machine
          if self._scp_data_length is None:
              data = self.get_software_version(255, 255, 0)
              self._scp_data_length = data.buffer_size
          return self._scp_data_length