docs: def write(self, filehandle, file_format):
          """Write :class:`~ctfile.ctfile.CTfile` data into file. 
  
          :param filehandle: File-like object.
          :param str file_format: Format to use to write data: ``ctfile`` or ``json``.
          :return: None.
          :rtype: :py:obj:`None`.
          """
          try:
              filehandle.write(self.writestr(file_format=file_format))
          except IOError:
              raise IOError('"filehandle" parameter must be writable.')