private boolean isGraphMLXSDPresent() {
            // when the graphml website goes down then tests won't pass - this allows the tests that rely on this
            // resource to conditionally run
            try {
                new URL("http://graphml.graphdrawing.org/xmlns/1.1/graphml-structure.xsd").openConnection().connect();
                return true;
            } catch (Exception ex) {
                return false;
            }
        }
Note: this is only a very lightweight test of writer/reader encoding. It is known that there are characters
which, when written by GraphMLWriter, cause parse errors for GraphMLReader. However, this happens uncommonly
enough that is not yet known which characters those are. Only need to execute this test with TinkerGraph
or other graphs that support user supplied identifiers.
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/structure/io/IoTest.java