@Override
  public Optional<Address> contractAddress() {
    if (isContractCreation()) {
      return Optional.of(Address.contractAddress(getSender(), getNonce()));
    }
    return Optional.empty();
  }
Return the list of transaction hashes extracted from the collection of Transaction passed as
argument

@param transactions a collection of transactions
@return the list of transaction hashes
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/core/Transaction.java