@Override
  public void becomeImmutable() {
    immutable = true;
  }
A map of the storage entries that were modified.

@return a map containing all entries that have been modified. This <b>may</b> contain entries
    with a value of 0 to signify deletion.
evm/src/main/java/org/hyperledger/besu/evm/worldstate/JournaledAccount.java