def add_node(self, v, **info):
    if (not (v in self.edges)):
        self.edges[v] = {}
    if (v in self.nodes):
        return
    self.nodes[v] = info
def add_node(self, v, **info):
    if (not (v in self.edges)):
        self.edges[v] = {}
    if (v in self.nodes):
        return
    self.nodes[v] = info