code: def extrinsic_events(network, previous_state, current_state, next_state,
                       indices=None, major_complex=None):
      
      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)
docs: 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.