You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: actions.go
    path of file: ./repos/goreportcard/vendor/gopkg.in/alecthomas/kingpin.v2
    
    the code of the file until where you have to start completion: package kingpin

// Action callback executed at various stages after all values are populated.
// The application, commands, arguments and flags all have co
    
func (a *actionMixin) applyPreActions(context *ParseContext) error {
	for _, preAction := range a.preActions {
		if err := preAction(context); err != nil {
			return err
		}
	}
	return nil
}