@staticmethod
def add_callback(callback, control_instance):
    """ Method to add a callback to the control instance when the controller
        trait is modified

        Parameters
        ----------
        callback: @function (mandatory)
            the function that will be called when a 'textChanged' signal is
            emited.
        control_instance: QFrame (mandatory)
            the control widget we want to validate
        """
    pass
