@staticmethod
def add_callback(callback, control_instance):
    """ Method to add a callback to the control instance when a 'userModification'
        signal is emited.

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