public Map<Integer, Schema> schemasById() {
    return schemasById;
  }
@Test
  public void testParseSchemaIdentifierFields() throws Exception {
    String data = readTableMetadataInputFile("TableMetadataV2Valid.json");
    TableMetadata parsed = TableMetadataParser.fromJson(data);
    assertThat(parsed.schemasById().get(0).identifierFieldIds()).isEmpty();
    assertThat(parsed.schemasById().get(1).identifierFieldIds()).containsExactly(1, 2);
  }