code: def true_events(network, previous_state, current_state, next_state,
                  indices=None, major_complex=None):
      
      # TODO: validate triplet of states
  
      if major_complex:
          nodes = major_complex.subsystem.node_indices
      elif indices:
          nodes = indices
      else:
          major_complex = compute.major_complex(network, current_state)
          nodes = major_complex.subsystem.node_indices
  
      return events(network, previous_state, current_state, next_state, nodes)
docs: Return all mechanisms that have true causes and true effects within the
      complex.
  
      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[Event]: List of true events in the major complex.