Returns the label that contains the inputed action.
        
        :return     <XDockActionLabel> || None

def labelForAction(self, action):
        """
        Returns the label that contains the inputed action.
        
        :return     <XDockActionLabel> || None
        """
        for label in self.actionLabels():
            if label.action() == action:
                return label
        return None