code: func actionDefinition() (*design.ActionDefinition, bool) {
  	a, ok := dslengine.CurrentDefinition().(*design.ActionDefinition)
  	if !ok {
  		dslengine.IncompatibleDSL()
  	}
  	return a, ok
  }
docs: // actionDefinition returns true and current context if it is an ActionDefinition,
  // nil and false otherwise.