code: def get_index(self, prefix=''):
          
          if prefix:
              prefixed = '%s_index' % prefix
          else:
              prefixed = 'index'
  
          if prefixed in self.__cli and self.__cli[prefixed]:
              index = self.__cli.get(prefixed)
              from_conf = False
          else:
              index = self.__config.get(prefixed)
              from_conf = True
  
          return self.__abspath(index, from_conf)
docs: Retrieve the absolute path to an index, according to
          `prefix`.
  
          Args:
              prefix: str, the desired prefix or `None`.
  
          Returns:
              str: An absolute path, or `None`