code: def directional_sia(subsystem, direction, unpartitioned_ces=None):
      
      if unpartitioned_ces is None:
          unpartitioned_ces = _ces(subsystem)
  
      c_system = ConceptStyleSystem(subsystem, direction)
      cuts = concept_cuts(direction, c_system.cut_indices, subsystem.node_labels)
  
      # Run the default SIA engine
      # TODO: verify that short-cutting works correctly?
      engine = ComputeSystemIrreducibility(
          cuts, c_system, unpartitioned_ces)
      return engine.run(config.PARALLEL_CUT_EVALUATION)
docs: Calculate a concept-style SystemIrreducibilityAnalysisCause or
      SystemIrreducibilityAnalysisEffect.