code: def __check_config_key(self, key):
          
          try:
              section, option = key.split('.')
          except (AttributeError, ValueError):
              return False
  
          if not section or not option:
              return False
  
          return section in Config.CONFIG_OPTIONS and\
              option in Config.CONFIG_OPTIONS[section]
docs: Check whether the key is valid.
  
          A valid key has the schema <section>.<option>. Keys supported
          are listed in CONFIG_OPTIONS dict.
  
          :param key: <section>.<option> key