public static SparqlGremlinPlugin instance() {
        return instance;
    }
{@link GremlinPlugin} implementation for {@code sparql-gremlin} that imports the key classes and interfaces required
to use SPARQL in TinkerPop.

@author Stephen Mallette (http://stephen.genoprime.com)
sparql-gremlin/src/main/java/org/apache/tinkerpop/gremlin/sparql/jsr223/SparqlGremlinPlugin.java