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

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