code: func (mf *MultiFlag) Parse(value string) error {
  	option, params := parseOptionParams(value)
  	if len(option) == 0 {
  		return errors.New("Option cannot be empty.")
  	}
  
  	mf.Selected = mf.GetOptionFor(option)
  	if mf.Selected == nil {
  		return fmt.Errorf("Invalid option: %v", option)
  	}
  	return mf.Selected.Run(params)
  }
docs: // Parse applies a value string to a MultiFlag.
  //
  // For example, if the value string is:
  // foo,option1=test
  //
  // Parse will identify the MultiFlag option named "foo" and have it parse the
  // string, "option1=test".