Converts the python list returned by self._txtinfo_to_python()
        to a NetworkX Graph object, which is then returned.

def _parse_txtinfo(self, data):
        """
        Converts the python list returned by self._txtinfo_to_python()
        to a NetworkX Graph object, which is then returned.
        """
        graph = self._init_graph()
        for link in data:
            graph.add_edge(link['source'],
                           link['target'],
                           weight=link['cost'])
        return graph