def example_networkx(ax=None, **options):
    """
    example using networks

    @param      ax          axis
    @param      options     look at the code
    @return                 ax
    """
    import networkx as nx
    import matplotlib.pyplot as plt
    G = nx.random_geometric_graph(200, 0.125)
    pos = nx.get_node_attributes(G, 'pos')
    dmin = 1
    ncenter = 0
    for n in pos:
        x, y = pos[n]
        d = (x - 0.5) ** 2 + (y - 0.5) ** 2
        if d < dmin:
            ncenter = n
            dmin = d
    p = nx.single_source_shortest_path_length(G, ncenter)
    if ax is None:
        _, ax = plt.subplots(nrows=1, ncols=1, figsize=options.get(
            'figsize', (5, 5)))
    nx.draw_networkx_edges(G, pos, nodelist=[ncenter], alpha=0.4, ax=ax)
    nx.draw_networkx_nodes(G, pos, nodelist=p.keys(), node_size=80, ax=ax)
    ax.set_xlim(-0.05, 1.05)
    ax.set_ylim(-0.05, 1.05)
    ax.axis('off')
    return ax
