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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 del_graph(self, name):
 """Remove all traces of a graph's existence from the database :arg name: name of an existing graph """

        # make sure the graph exists before deleting anything
        self.get_graph(name)
        self.query.del_graph(name)
        if name in self._graph_objs:
            del self._graph_objs[name]