public static FactoryBuilder newFactoryBuilder() {
    return new FactoryBuilder();
  }
@Test void injectKindFormats_cantBeSame() {
    assertThatThrownBy(() -> B3Propagation.newFactoryBuilder()
      .injectFormats(Span.Kind.CLIENT, Format.MULTI, Format.MULTI))
      .isInstanceOf(IllegalArgumentException.class);
  }