@CanIgnoreReturnValue
    @Override
    public Builder<E> addAll(Iterator<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    /**
     * If the specified collection is backed by an ObjectCountHashMap, it will be much more
     * efficient to iterate over it by index rather than an entry iterator, which will need to
     * allocate an object for each entry, so we check for that.
     */

        return entry.getValue();
      }
    };
  }

  /**
   * Returns an immutable map instance containing the given entries. Internally, the returned map
   * will be backed by an {@link EnumMap}.
   *
   * <p>The iteration order of the returned map follows the enum's iteration order, not the order in
   * which the elements appear in the given map.
   *

import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.EnumSet;
import javax.annotation.CheckForNull;

/**
 * Implementation of {@link ImmutableSet} backed by a non-empty {@link java.util.EnumSet}.
 *
 * @author Jared Levy
 */
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization

      }
      // The cast is safe because of the hasPeeked check.
      return uncheckedCastNullableTToT(peekedElement);
    }
  }

  /**
   * Returns a {@code PeekingIterator} backed by the given iterator.
   *
   * <p>Calls to the {@code peek} method with no intervening calls to {@code next} do not affect the
   * iteration, and hence return the same object each time. A subsequent call to {@code next} is