default public Object convertId(final Object id, final Class<? extends Element> c) {
        return id;
    }
Converts an identifier from a test to an identifier accepted by the {@link Graph} instance.  Test that try to
utilize an Element identifier will pass it to this method before usage.  This method should be sure to
be consistent in the return value such that calling it with "x" should always return the same transformed
value.
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/GraphProvider.java