public static FileMetadata fromJson(String json) {
    return JsonUtil.parse(json, FileMetadataParser::fromJson);
  }
@Test
  public void testBadBlobs() {
    assertThatThrownBy(() -> FileMetadataParser.fromJson("{\"blobs\": {}}"))
        .isInstanceOf(IllegalArgumentException.class)
        .hasMessage("Cannot parse blobs from non-array: {}");
  }