code: static Key[] toNativeKeys(List<DatastoreKey> keys) {
      Key[] nativeKeys = new Key[keys.size()];
      for (int i = 0; i < keys.size(); i++) {
        nativeKeys[i] = keys.get(i).nativeKey();
      }
      return nativeKeys;
    }
docs: Converts/Unwraps the given list of {@link DatastoreKey} objects into an array of native
  {@link Key}s.
  
  @param keys
  the list of {@link DatastoreKey} objects
  @return the native keys