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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 action_checkbox(self, obj):
 """ A list_display column containing a checkbox widget. """

        if self.check_concurrent_action:
            return helpers.checkbox.render(helpers.ACTION_CHECKBOX_NAME,
                                           force_text("%s,%s" % (obj.pk,
                                                                 get_revision_of_object(obj))))
        else:  # pragma: no cover
            return super(ConcurrencyActionMixin, self).action_checkbox(obj)