public P<V> clone() {
        try {
            return (P<V>) super.clone();
        } catch (final CloneNotSupportedException e) {
            throw new IllegalStateException(e.getMessage(), e);
        }
    }
Gets the current value to be passed to the predicate for testing.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/P.java