@staticmethod
def _graph_indices(T, changepoints):
    """Describes which graphs are active for each time
        by returning a list with the graphs indices

        Parameters
        ----------
        T : int
            number of total timesteps
        changepoints : list[int]
            list of changepoint indices

        Yields
        ------
        Graph indices for all t < T
        """
    graph = count = 0
    for cp in changepoints:
        while count < cp:
            count += 1
            yield graph
        graph += 1
    while count < T:
        count += 1
        yield graph
