derivedSuites.add(createSubsetSuite(parentBuilder, Bound.EXCLUSIVE, Bound.NO_BOUND));
      derivedSuites.add(createSubsetSuite(parentBuilder, Bound.EXCLUSIVE, Bound.EXCLUSIVE));
      derivedSuites.add(createSubsetSuite(parentBuilder, Bound.EXCLUSIVE, Bound.INCLUSIVE));
      derivedSuites.add(createSubsetSuite(parentBuilder, Bound.INCLUSIVE, Bound.INCLUSIVE));
    }

    }

    @Override
    public NavigableSet<E> headSet(@ParametricNullness E toElement, boolean inclusive) {
      return new NavigableElementSet<>(
          multiset().headMultiset(toElement, BoundType.forBoolean(inclusive)));
    }

    @Override
    public NavigableSet<E> tailSet(@ParametricNullness E fromElement, boolean inclusive) {
      return new NavigableElementSet<>(

      derivedSuites.add(createSubMultisetSuite(parentBuilder, Bound.INCLUSIVE, Bound.EXCLUSIVE));
      derivedSuites.add(createSubMultisetSuite(parentBuilder, Bound.INCLUSIVE, Bound.INCLUSIVE));
    }

    return derivedSuites;
  }

  private TestSuite createSubMultisetSuite(
      SortedMultisetTestSuiteBuilder<E> parentBuilder, Bound from, Bound to) {
    TestMultisetGenerator<E> delegate =

  OPEN(false),
  CLOSED(true);

  final boolean inclusive;

  BoundType(boolean inclusive) {
    this.inclusive = inclusive;
  }

  /** Returns the bound type corresponding to a boolean value for inclusivity. */
  static BoundType forBoolean(boolean inclusive) {
    return inclusive ? CLOSED : OPEN;
  }

      if (from == Bound.NO_BOUND && to == Bound.EXCLUSIVE) {
        return set.headSet(lastExclusive);
      } else if (from == Bound.INCLUSIVE && to == Bound.NO_BOUND) {
        return set.tailSet(firstInclusive);
      } else if (from == Bound.INCLUSIVE && to == Bound.EXCLUSIVE) {
        return set.subSet(firstInclusive, lastExclusive);
      } else {
        throw new IllegalArgumentException();
      }

    return subSet(fromElement, true, toElement, false);
  }

  @Override
  public NavigableSet<E> headSet(@ParametricNullness E toElement, boolean inclusive) {
    return delegate().headSet(toElement, inclusive);
  }

  /**
   * A sensible definition of {@link #headSet(Object)} in terms of the {@link #headSet(Object,

		between the lower and upper bound specified by the Range Query. Range
		Queries can be inclusive or exclusive of the upper and lower bounds.
		If you want to find documents whose content_length fields have values
		between 1000 and 10000, inclusive, you can enter:
		<pre>content_length:[1000 TO 10000]</pre>
		If you want to exclude the upper and lower bounds, use "{}".
	</dd>
	<dt>Boost</dt>

      for (List<Integer> contents : SAMPLE_INPUTS) {
        for (int i = 0; i < 10; i++) {
          for (boolean inclusive : ImmutableList.of(true, false)) {
            assertEquals(
                filter(createUnfiltered(contents).headSet(i, inclusive), EVEN),
                filter(createUnfiltered(contents), EVEN).headSet(i, inclusive));
          }
        }
      }
    }

    public void testNavigableTailSet() {

  OPEN(false),
  CLOSED(true);

  final boolean inclusive;

  BoundType(boolean inclusive) {
    this.inclusive = inclusive;
  }

  /** Returns the bound type corresponding to a boolean value for inclusivity. */
  static BoundType forBoolean(boolean inclusive) {
    return inclusive ? CLOSED : OPEN;
  }

      derivedSuites.add(createSubsetSuite(parentBuilder, Bound.EXCLUSIVE, Bound.NO_BOUND));
      derivedSuites.add(createSubsetSuite(parentBuilder, Bound.EXCLUSIVE, Bound.EXCLUSIVE));
      derivedSuites.add(createSubsetSuite(parentBuilder, Bound.EXCLUSIVE, Bound.INCLUSIVE));
      derivedSuites.add(createSubsetSuite(parentBuilder, Bound.INCLUSIVE, Bound.INCLUSIVE));
    }