@Override
    public boolean remove(final Object arg) {
        final int i = indexOf(arg);
        if (i < 0) {
            return false;
        }
        delete(i);
        return true;
    }
This is an extremely expensive implementation of
{@link Set#containsAll(Collection)}. It is implemented as O(n**2).
vespajlib/src/main/java/com/yahoo/collections/TinyIdentitySet.java