def find_removal_edges(g1, g2):
    """
    Given a graph in snapshot t and another graph in snapshot t+1, find the removal edges, i.e. the ones that in G_t but
    not in G_(t+1).
    :param g1: Graph in snapshot t
    :param g2: Graph in snapshot t+1
    :return: List of removal edges
    """
    edges_1 = set(g1.edges())
    new_edges_1 = []
    for e in edges_1:
        new_edges_1.append(e if int(e[0]) < int(e[1]) else (e[1], e[0]))
    edges_2 = set(g2.edges())
    new_edges_2 = []
    for e in edges_2:
        new_edges_2.append(e if int(e[0]) < int(e[1]) else (e[1], e[0]))
    return list(set(new_edges_1) - set(new_edges_2))