docs: def platedir(self, filetype, **kwargs):
          """Returns plate subdirectory in :envvar:`PLATELIST_DIR` of the form: ``NNNNXX/NNNNNN``.
  
          Parameters
          ----------
          filetype : str
              File type parameter.
          plateid : int or str
              Plate ID number.  Will be converted to int internally.
  
          Returns
          -------
          platedir : str
              Plate directory in the format ``NNNNXX/NNNNNN``.
          """
          plateid = int(kwargs['plateid'])
          plateid100 = plateid // 100
          subdir = "{:0>4d}".format(plateid100) + "XX"
          return os.path.join(subdir, "{:0>6d}".format(plateid))