public default <S> S getSafeScopeValue(final Pop pop, final Object key, final Traverser.Admin<?> traverser) {
        try {
            return getScopeValue(pop, key, traverser);
        } catch (KeyNotFoundException nfe) {
            throw new IllegalArgumentException(nfe.getMessage(), nfe);
        }
    }
Calls {@link #getScopeValue(Pop, Object, Traverser.Admin)} but throws an unchecked {@code IllegalStateException}
if the key cannot be found.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/Scoping.java