code: def _data_to_sign(self) -> bytes:
          
          packed = pack_reward_proof(
              canonical_identifier=CanonicalIdentifier(
                  chain_identifier=self.balance_proof.chain_id,
                  token_network_address=self.balance_proof.token_network_address,
                  channel_identifier=self.balance_proof.channel_identifier,
              ),
              reward_amount=self.reward_amount,
              nonce=self.balance_proof.nonce,
          )
          return packed
docs: Return the binary data to be/which was signed