code: def format_map(self, format_string, mapping):
          
          return self.vformat(format_string, args=None, kwargs=mapping)
docs: format a string by a map
  
          Args:
              format_string(str): A format string
              mapping(dict): A map to format the string
  
          Returns:
              A formatted string.
  
          Raises:
              KeyError: if key is not provided by the given map.