docs: def write(self, filehandle, file_format):
          """Write :class:`~nmrstarlib.nmrstarlib.StarFile` data into file.
  
          :param filehandle: file-like object.
          :type filehandle: :py:class:`io.TextIOWrapper`
          :param str file_format: Format to use to write data: `nmrstar`, `cif`, or `json`.
          :return: None
          :rtype: :py:obj:`None`
          """
          try:
              if file_format == "json":
                  json_str = self._to_json()
                  filehandle.write(json_str)
              elif file_format == "nmrstar" and isinstance(self, NMRStarFile):
                  nmrstar_str = self._to_star()
                  filehandle.write(nmrstar_str)
              elif file_format == "cif" and isinstance(self, CIFFile):
                  cif_str = self._to_star()
                  filehandle.write(cif_str)
              else:
                  raise TypeError("Unknown file format.")
          except IOError:
              raise IOError('"filehandle" parameter must be writable.')
          filehandle.close()