public Object apply(final Object a, final Object b) {
            return b;
        }
The new incoming value (i.e. the second value to the function) is returned unchanged result in the assignment
of that value to the object of the {@code Operator}.

@since 3.1.0-incubating
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/Operator.java