/**
 * A filtering provider that uses a spec to filter the value of another provider.
 **/
public class FilteringProvider<T> extends AbstractMinimalProvider<T> {

    protected final ProviderInternal<T> provider;
    protected final Spec<? super T> spec;

    public FilteringProvider(
        ProviderInternal<T> provider,
        Spec<? super T> spec
    ) {
        this.spec = spec;

        return new TransformBackedProvider<>(null, this, transformer);
    }

    @Override
    public ProviderInternal<T> filter(final Spec<? super T> spec) {
        return new FilteringProvider<>(this, spec);
    }

    @Override
    public <S> Provider<S> flatMap(final Transformer<? extends @org.jetbrains.annotations.Nullable Provider<? extends S>, ? super T> transformer) {