code: static <K, V> MapMakerInternalMap<K, V, ? extends InternalEntry<K, V, ?>, ?> create(
        MapMaker builder) {
      if (builder.getKeyStrength() == Strength.STRONG
          && builder.getValueStrength() == Strength.STRONG) {
        return new MapMakerInternalMap<>(builder, StrongKeyStrongValueEntry.Helper.<K, V>instance());
      }
      if (builder.getKeyStrength() == Strength.STRONG
          && builder.getValueStrength() == Strength.WEAK) {
        return new MapMakerInternalMap<>(builder, StrongKeyWeakValueEntry.Helper.<K, V>instance());
      }
      if (builder.getKeyStrength() == Strength.WEAK
          && builder.getValueStrength() == Strength.STRONG) {
        return new MapMakerInternalMap<>(builder, WeakKeyStrongValueEntry.Helper.<K, V>instance());
      }
      if (builder.getKeyStrength() == Strength.WEAK && builder.getValueStrength() == Strength.WEAK) {
        return new MapMakerInternalMap<>(builder, WeakKeyWeakValueEntry.Helper.<K, V>instance());
      }
      throw new AssertionError();
    }
docs: Returns a fresh {@link MapMakerInternalMap} as specified by the given {@code builder}.