code: def parse(self, arguments):
      
      new_values = self._parse(arguments)
      if self.present:
        self.value.extend(new_values)
      else:
        self.value = new_values
      self.present += len(new_values)
docs: Parses one or more arguments with the installed parser.
  
      Args:
        arguments: a single argument or a list of arguments (typically a
          list of default values); a single argument is converted
          internally into a list containing one item.