public static Builder builder() {
    return new Builder();
  }
@Test
  public void testBuilderDoesNotBuildInvalidRequests() {
    assertThatThrownBy(() -> GetNamespaceResponse.builder().withNamespace(null).build())
        .isInstanceOf(NullPointerException.class)
        .hasMessage("Invalid namespace: null");

    assertThatThrownBy(() -> GetNamespaceResponse.builder().setProperties(null).build())
        .isInstanceOf(NullPointerException.class)
        .hasMessage("Invalid properties map: null");

    Map<String, String> mapWithNullKey = Maps.newHashMap();
    mapWithNullKey.put(null, "hello");
    assertThatThrownBy(() -> GetNamespaceResponse.builder().setProperties(mapWithNullKey).build())
        .isInstanceOf(IllegalArgumentException.class)
        .hasMessage("Invalid property: null");

    Map<String, String> mapWithMultipleNullValues = Maps.newHashMap();
    mapWithMultipleNullValues.put("a", null);
    mapWithMultipleNullValues.put("b", "b");
    assertThatThrownBy(
            () -> GetNamespaceResponse.builder().setProperties(mapWithMultipleNullValues).build())
        .isInstanceOf(IllegalArgumentException.class)
        .hasMessage("Invalid value for properties [a]: null");
  }