OneSizeTestContainerGenerator<Map<K, V>, Entry<K, V>> mapGenerator) {
    TestContainerGenerator<Map<K, V>, Entry<K, V>> generator = mapGenerator.getInnerGenerator();
    if (generator instanceof TestSortedMapGenerator
        && ((TestSortedMapGenerator<K, V>) generator).create().keySet() instanceof SortedSet) {
      return new MapSortedKeySetGenerator<>(mapGenerator);
    } else {
      return new MapKeySetGenerator<>(mapGenerator);
    }
  }

import com.google.common.collect.testing.NavigableSetTestSuiteBuilder;
import com.google.common.collect.testing.SampleElements;
import com.google.common.collect.testing.TestSortedMapGenerator;
import com.google.common.collect.testing.TestStringSetGenerator;
import com.google.common.collect.testing.TestStringSortedSetGenerator;
import com.google.common.collect.testing.features.CollectionFeature;