def inter_event_time_distribution(G, u=None, v=None):
    """Return the distribution of inter event time.
     If u and v are None the dynamic graph intere event distribution is returned.
     If u is specified the inter event time distribution of interactions involving u is returned.
     If u and v are specified the inter event time distribution of (u, v) interactions is returned

     Parameters
     ----------
     G : graph
            A DyNetx graph.
     u : node id
     v : node id

     Returns
     -------

     nd : dictionary
         A dictionary from inter event time to number of occurrences
    """
    return G.inter_event_time_distribution(u, v)