* that tests equivalence using their lengths:
   *
   * {@snippet :
   * equiv.wrap("a").equals(equiv.wrap("b")) // true
   * equiv.wrap("a").equals(equiv.wrap("hello")) // false
   * }
   *
   * <p>Note in particular that an equivalence wrapper is never equal to the object it wraps.
   *
   * {@snippet :
   * equiv.wrap(obj).equals(obj) // always false
   * }
   *
   * @since 10.0
   */

 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software

// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

it, or that there are particular complexities that you should know about before
starting the implementation. There are often a number of ways to fix a problem
and it is important to find the right approach before spending time on a PR
that cannot be merged.

We add the `help wanted` label to existing GitHub issues for which community
contributions are particularly welcome, and we use the `good first issue` label

 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software

   * {@code key}. Equivalent to (but expected to be more efficient than):
   *
   * {@snippet :
   * for (V value : values) {
   *   put(key, value);
   * }
   * }
   *
   * <p>In particular, this is a no-op if {@code values} is empty.
   *
   * @return {@code true} if the multimap changed
   */
  @CanIgnoreReturnValue
  boolean putAll(@ParametricNullness K key, Iterable<? extends V> values);

// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

    @Override
    protected Map<Integer, Character> getValueNotInPopulatedMap() {
      return ImmutableMap.of();
    }

    /**
     * The version of this test supplied by {@link MapInterfaceTest} fails for this particular map
     * implementation, because {@code map.get()} returns a view collection that changes in the
     * course of a call to {@code remove()}. Thus, the expectation doesn't hold that {@code