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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 clear_graph(identifier=None):
 """ Clean up a graph by removing it :param identifier: Root identifier of the graph :return: """

    graph = get_graph()
    if identifier:
        graph.destroy(identifier)
    try:
        graph.close()
    except:
        warn("Unable to close the Graph")