public static TableSchema of(Column... columns) {
    return new AutoValue_TableSchema(Arrays.asList(columns));
  }
@Test
  public void testParseNullableEnum16() {
    Map<String, Integer> enumValues =
        ImmutableMap.of(
            "a", -1,
            "b", 0,
            "c", 42);

    assertEquals(
        ColumnType.enum16(enumValues).withNullable(true),
        ColumnType.parse("Nullable(Enum16('a' = -1, 'b' = 0, 'c' = 42))"));
  }