@Override
  public boolean containsKey(final SegmentIdentifier segmentId, final byte[] key)
      throws StorageException {
    return get(segmentId, key).isPresent();
  }
Constructor which takes an explicit backing map for the layered key value storage.

@param map the backing map
@param parent the parent key value storage for this layered storage.
services/kvstore/src/main/java/org/hyperledger/besu/services/kvstore/LayeredKeyValueStorage.java