code: def handle_offchain_secretreveal(
          target_state: TargetTransferState,
          state_change: ReceiveSecretReveal,
          channel_state: NettingChannelState,
          pseudo_random_generator: random.Random,
          block_number: BlockNumber,
  ) -> TransitionResult[TargetTransferState]:
      
      valid_secret = is_valid_secret_reveal(
          state_change=state_change,
          transfer_secrethash=target_state.transfer.lock.secrethash,
          secret=state_change.secret,
      )
      has_transfer_expired = channel.is_transfer_expired(
          transfer=target_state.transfer,
          affected_channel=channel_state,
          block_number=block_number,
      )
  
      if valid_secret and not has_transfer_expired:
          channel.register_offchain_secret(
              channel_state=channel_state,
              secret=state_change.secret,
              secrethash=state_change.secrethash,
          )
  
          route = target_state.route
          message_identifier = message_identifier_from_prng(pseudo_random_generator)
          target_state.state = TargetTransferState.OFFCHAIN_SECRET_REVEAL
          target_state.secret = state_change.secret
          recipient = route.node_address
  
          reveal = SendSecretReveal(
              recipient=recipient,
              channel_identifier=CHANNEL_IDENTIFIER_GLOBAL_QUEUE,
              message_identifier=message_identifier,
              secret=target_state.secret,
          )
  
          iteration = TransitionResult(target_state, [reveal])
  
      else:
          # TODO: event for byzantine behavior
          iteration = TransitionResult(target_state, list())
  
      return iteration
docs: Validates and handles a ReceiveSecretReveal state change.