docs: def mmcif(self):
          """ Filepath for mmcif file associated with code.
  
          Notes
          -----
          Downloads mmcif file if not already present.
  
          Returns
          -------
          mmcif_file : str
              Filepath for the mmcif file.
          """
          mmcif_dir = os.path.join(self.parent_dir, 'mmcif')
          if not os.path.exists(mmcif_dir):
              os.makedirs(mmcif_dir)
          mmcif_file_name = '{0}.cif'.format(self.code)
          mmcif_file = os.path.join(mmcif_dir, mmcif_file_name)
          if not os.path.exists(mmcif_file):
              get_mmcif(code=self.code, outfile=mmcif_file)
          return mmcif_file