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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 GetFarthestNode(self, gr, node):
 """node is start node"""

        # Remember: weights are negative
        distance = minmax.shortest_path_bellman_ford(gr, node)[1]

        # Find the farthest node, which is end of track
        min_key = None
        for key, value in distance.iteritems():
            if min_key is None or value < distance[min_key]:
                min_key = key

        return min_key