'Return True if the graph contains the node n.
Parameters
n : node
Examples
>>> G = nx.path_graph(3)  # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.has_node(0)
True
It is more readable and simpler to use
>>> 0 in G
True'

def has_node(self, n):

    try:
        return (n in self._node)
    except TypeError:
        return False
