code: def read_state_file(self, state_file):
          
          try:
              fh = open(state_file, 'r')
              state = json.load(fh)
              self.vpc_id = state['vpcID']
              self.sg_id = state['sgID']
              self.sn_ids = state['snIDs']
              self.instances = state['instances']
          except Exception as e:
              logger.debug("Caught exception while reading state file: {0}".format(e))
              raise e
          logger.debug("Done reading state from the local state file.")
docs: Read the state file, if it exists.
  
          If this script has been run previously, resource IDs will have been written to a
          state file. On starting a run, a state file will be looked for before creating new
          infrastructure. Information on VPCs, security groups, and subnets are saved, as
          well as running instances and their states.
  
          AWS has a maximum number of VPCs per region per account, so we do not want to
          clutter users' AWS accounts with security groups and VPCs that will be used only
          once.