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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 get_tom(self, node):
 """ Convert the given node into a Temporal Occurrence Model object. :param node: a node of kind poissonTOM or brownianTOM :returns: a :class:`openquake.hazardlib.mfd.EvenlyDiscretizedMFD.` or :class:`openquake.hazardlib.mfd.TruncatedGRMFD` instance """

        if 'tom' in node.attrib:
            tom_cls = tom.registry[node['tom']]
        else:
            tom_cls = tom.registry['PoissonTOM']
        return tom_cls(time_span=self.investigation_time,
                       occurrence_rate=node.get('occurrence_rate'))