Re-implements the orb.Column.valueFromString method to
        lookup a reference object based on the given value.

        :param value: <str>
        :param context: <orb.Context> || None

        :return: <orb.Model> || None

def valueFromString(self, value, context=None):
        """
        Re-implements the orb.Column.valueFromString method to
        lookup a reference object based on the given value.

        :param value: <str>
        :param context: <orb.Context> || None

        :return: <orb.Model> || None
        """
        model = self.referenceModel()
        return model(value, context=context)