List<Feature<?>> features = new ArrayList<>(parentBuilder.getFeatures());
    Set<Method> suppressing = new HashSet<>(parentBuilder.getSuppressedTests());
    features.add(CollectionFeature.SUBSET_VIEW);
    if (features.remove(CollectionFeature.ALLOWS_NULL_VALUES)) {
      // the null value might be out of bounds, so we can't always construct a subset with nulls
      features.add(CollectionFeature.ALLOWS_NULL_QUERIES);

    List<Feature<?>> features = new ArrayList<>(parentBuilder.getFeatures());
    Set<Method> suppressing = new HashSet<>(parentBuilder.getSuppressedTests());
    features.add(CollectionFeature.SUBSET_VIEW);
    if (features.remove(CollectionFeature.ALLOWS_NULL_VALUES)) {
      // the null value might be out of bounds, so we can't always construct a subset with nulls
      features.add(CollectionFeature.ALLOWS_NULL_QUERIES);

import static com.google.common.collect.testing.features.CollectionFeature.KNOWN_ORDER;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;

import static com.google.common.collect.testing.features.CollectionFeature.SERIALIZABLE_INCLUDING_VIEWS;
import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.ListFeature.SUPPORTS_ADD_WITH_INDEX;
import static com.google.common.collect.testing.features.ListFeature.SUPPORTS_REMOVE_WITH_INDEX;

But at some point, there was no other option than creating something that provided all these features, taking the best ideas from previous tools, and combining them in the best way possible, using language features that weren't even available before (Python 3.6+ type hints).

          parentBuilder) {
    Set<Feature<?>> features = computeMultimapAsMapGetFeatures(parentBuilder.getFeatures());
    if (Collections.disjoint(features, EnumSet.allOf(CollectionSize.class))) {
      return new TestSuite();
    } else {
      return SetTestSuiteBuilder.using(
              new MultimapAsMapGetGenerator<K, V>(parentBuilder.getSubjectGenerator()))
          .withFeatures(features)

import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.SUPPORTS_PUT;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.testing.features.CollectionSize;
import com.google.common.collect.testing.features.MapFeature;
import java.util.List;
import java.util.Map.Entry;

 */

package com.google.common.collect.testing.features;

import static com.google.common.collect.testing.Helpers.copyToSet;

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Map;
import java.util.Set;

/**
 * Optional features of classes derived from {@code Map}.
 *

import static com.google.common.collect.testing.features.CollectionFeature.KNOWN_ORDER;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
import static com.google.common.collect.testing.features.CollectionSize.ONE;
import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;

 */

package com.google.common.collect.testing.google;

import static com.google.common.collect.testing.Helpers.assertEmpty;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;
import static com.google.common.collect.testing.features.MapFeature.SUPPORTS_REMOVE;
import static com.google.common.collect.testing.google.GoogleHelpers.assertEmpty;