code: protected String resolveNamespace(String namespace, String name) {
      return resolveNamespace(namespace, name, null);
    }
docs: Checks whether the Hive table {@code namespace.name} exists or if
  {@code default.name} exists and should be used.
  
  @param namespace the requested namespace
  @param name the table name
  @return if namespace.name exists, namespace. if not and default.name
  exists, then default. {@code null} otherwise.