docs: def delete(filename, conn=None):
      """
      deletes a file
      filename being a value in the "id" key
      :param filename: <str>
      :param conn: <rethinkdb.DefaultConnection>
      :return: <dict>
      """
      return RBF.filter((r.row[PRIMARY_FIELD] == filename) | (r.row[PARENT_FIELD] == filename)).delete().run(conn)