text: import simpy
  import logging
  from .num_spec import NumSpec
  from .structure_item import StructureItem
  
  
  class Function(StructureItem):
      """
      A Function is a transformation that accepts one or more inputs (items)
      and transforms them into outputs (items).
      """
  
      def __init__(self, env: simpy.Environment, logger: logging.Logger,
                   construct_id: str, systemModel: dict, structureItem: dict):
  
          # Get call structure function index
          cs_function_index = systemModel['data']['callStructureIndex'][structureItem['referenceID']]
          # Check if function decomposition exists
          function_structure = systemModel['data']['cpsSystemModel']['callStructure'][cs_function_index]
          if function_structure['structure']['structure'] is not None:
              # Decompose structure for Function main Branch
              super(Function, self).__init__(env, logger,
                              construct_id, systemModel, function_structure['structure'])
          else:
              super(Function, self).__init__(env, logger,
                              construct_id, systemModel, structureItem)
          self.structureType = "Function"
          self.name = structureItem['referenceName']
  
          # **** Need to retrieve duration and timeout from systemModel ****
          self.duration = NumSpec()
          self.timeout = NumSpec()
  
          # Triggers / Outputs / Resources for the Function
          self.triggeredBy = []
          self.outputs = []
          function_index = systemModel['data']['systemModelIndex'][structureItem['referenceID']]
          function = systemModel['data']['cpsSystemModel']['function'][function_index['entity_index']]
  
          for item in function['relations']['triggeredBy']:
              self.triggeredBy.append(systemModel['data']['itemIndex'][item['itemTarget']['id']])
  
          for item in function['relations']['outputs']:
              self.outputs.append(systemModel['data']['itemIndex'][item['itemTarget']['id']])
  
  
      def simulate(self):
          """
          Setup the Simpy simulation for a Function
          """
  
          self.log_start()
  
          # Check for function decomposition
          if len(self.structureItems) == 0:
  
              self.wait_trigger()
              self.begin()
              self.aquire_resources()
  
              yield self.env.timeout(self.duration.getValue())
  
              self.release_resources()
              self.produce_resources()
              self.output_items()
              self.exit()
              self.end()
          else:
              # Simulate decomposition
              for struct in self.structureItems:
                  yield(self.env.process(struct.simulate()))
  
          self.log_end()
  
      def wait_trigger(self):
          pass
  
      def aquire_resources(self):
          pass
  
      def release_resources(self):
          pass
  
      def produce_resources(self):
          pass
  
      def output_items(self):
          pass
  
      def begin(self):
          """
          Begin Logic is executed at the very beginning of function execution
          (after enablement and triggering but before resources are acquired).
          """
          return
  
      def exit(self):
          """
          Exit Logic determines which exit to use for a multi-exit function.
          If the exit logic is empty, the probabilities associated with the
          exits are used to choose the exit.
          """
          return
  
      def end(self):
          """
          End Logic is executed at the very end of function execution
          (after resources are produced and items are output).
          """
          return
  