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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 show_help(self, plugin=None, no_url_callback=None):
 """See `~ginga.GingaPlugin` for usage of optional keywords."""

        if not Widgets.has_webkit:
            return

        self.fv.nongui_do(self._download_doc, plugin=plugin,
                          no_url_callback=no_url_callback)