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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 update_version_descriptor(self, task, releasetype, descriptor, verbrowser, commentbrowser):
 """Update the versions in the given browser :param task: the task of the taskfiles :type task: :class:`djadapter.models.Task` | None :param releasetype: the releasetype :type releasetype: str|None :param descriptor: the descirptor :type descriptor: str|None :param verbrowser: the browser to update (the version browser) :type verbrowser: :class:`jukeboxcore.gui.widgets.browser.AbstractTreeBrowser` :param commentbrowser: the comment browser to update :type commentbrowser: :class:`jukeboxcore.gui.widgets.browser.AbstractTreeBrowser` :returns: None :rtype: None :raises: None """

        if task is None:
            null = treemodel.TreeItem(None)
            verbrowser.set_model(treemodel.TreeModel(null))
            return
        m = self.create_version_model(task, releasetype, descriptor)
        verbrowser.set_model(m)
        commentbrowser.set_model(m)