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'))