private List<FieldSchema> convertToFieldSchemas(List<MFieldSchema> mkeys) {
    List<FieldSchema> keys = null;
    if (mkeys != null) {
      keys = new ArrayList<>();
      for (MFieldSchema part : mkeys) {
        keys.add(new FieldSchema(part.getName(), part.getType(), part
            .getComment()));
      }
    }
    return keys;
  }
Makes shallow copy of a map to avoid DataNucleus mucking with our objects.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/ObjectStore.java