Permissions perms = new Permissions();

    AdjustablePolicy(Permission... permissions) {
      for (Permission permission : permissions) perms.add(permission);
    }

    void addPermission(Permission perm) {
      perms.add(perm);
    }

    void clearPermissions() {
      perms = new Permissions();
    }

    @Override

    }
  }

  /**
   * An {@link AbstractMultiset} with additional default implementations, some of them linear-time
   * implementations in terms of {@code elementSet} and {@code entrySet}.
   */
  private abstract static class ViewMultiset<E extends @Nullable Object>
      extends AbstractMultiset<E> {
    @Override
    public int size() {