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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def isVisible(self, instance, mode='view', default=None, field=None):
 """ This function returns the visibility of the widget depending on whether the rejection workflow is enabled or not. """

        vis = super(RejectionWidget, self).isVisible(
            instance=instance, mode=mode, default=default, field=field)
        if instance.bika_setup.isRejectionWorkflowEnabled():
            return vis
        else:
            return 'invisible'