def extrinsic_events(network, previous_state, current_state, next_state,
                     indices=None, major_complex=None):
    """Set of all mechanisms that are in the major complex but which have true
    causes and effects within the entire network.

    Args:
        network (Network): The network to analyze.
        previous_state (tuple[int]): The state of the network at ``t - 1``.
        current_state (tuple[int]): The state of the network at ``t``.
        next_state (tuple[int]): The state of the network at ``t + 1``.

    Keyword Args:
        indices (tuple[int]): The indices of the major complex.
        major_complex (AcSystemIrreducibilityAnalysis): The major complex. If
            ``major_complex`` is given then ``indices`` is ignored.

    Returns:
        tuple(actions): List of extrinsic events in the major complex.
    """
    if major_complex:
        mc_nodes = major_complex.subsystem.node_indices
    elif indices:
        mc_nodes = indices
    else:
        major_complex = compute.major_complex(network, current_state)
        mc_nodes = major_complex.subsystem.node_indices

    mechanisms = list(utils.powerset(mc_nodes, nonempty=True))
    all_nodes = network.node_indices

    return events(network, previous_state, current_state, next_state,
                  all_nodes, mechanisms=mechanisms)
Set of all mechanisms that are in the major complex but which have true
    causes and effects within the entire network.

    Args:
        network (Network): The network to analyze.
        previous_state (tuple[int]): The state of the network at ``t - 1``.
        current_state (tuple[int]): The state of the network at ``t``.
        next_state (tuple[int]): The state of the network at ``t + 1``.

    Keyword Args:
        indices (tuple[int]): The indices of the major complex.
        major_complex (AcSystemIrreducibilityAnalysis): The major complex. If
            ``major_complex`` is given then ``indices`` is ignored.

    Returns:
        tuple(actions): List of extrinsic events in the major complex.