import java.io.Serializable;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Issue3036 {

    public Set<MyInnerClass> getDsData() {
        throw new RuntimeException();
    }

    public static class MyInnerClass {
        public int getKeyTag() {
            return 5;
        }

        public String getDigest() {
            return "";
        }
    }

    private void write(Stream<MyInnerClass> stream) {
        Function<MyInnerClass, ImmutableMap<String, ? extends Serializable>> mapper =
                dsData1 ->
                        ImmutableMap.of(
                                "keyTag", dsData1.getKeyTag(),
                                "digest", dsData1.getDigest());

        List<Map<String, ?>> dsData =
                getDsData().stream()
                        .map(
                                dsData1 ->
                                        ImmutableMap.of(
                                                "keyTag", dsData1.getKeyTag(),
                                                "digest", dsData1.getDigest()))
                        .collect(Collectors.toList());
    }

    public static class ImmutableMap<K, V> extends HashMap<K, V> {
        public static <K, V> ImmutableMap<K, V> of(K k1, V v1, K k2, V v2) {
            throw new RuntimeException();
        }
    }
}