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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 build_arbitrary_mfd(mfd):
 """ Parses the arbitrary MFD as a Node :param mfd: MFD as instance of :class: `openquake.hazardlib.mfd.arbitrary.ArbitraryMFD` :returns: Instance of :class:`openquake.baselib.node.Node` """

    magnitudes = Node("magnitudes", text=mfd.magnitudes)
    occur_rates = Node("occurRates", text=mfd.occurrence_rates)
    return Node("arbitraryMFD", nodes=[magnitudes, occur_rates])