docs: def build_action(self, runnable, regime, action):
          """
          Build event handler action code.
  
          @param action: Event handler action object
          @type action: lems.model.dynamics.Action
  
          @return: Generated action code
          @rtype: string
          """
  
          if isinstance(action, StateAssignment):
              return self.build_state_assignment(runnable, regime, action)
          if isinstance(action, EventOut):
              return self.build_event_out(action)
          if isinstance(action, Transition):
              return self.build_transition(action)
          else:
              return ['pass']