public static CoreGremlinPlugin instance() {
        return INSTANCE;
    }
This module is required for a {@code ScriptEngine} to be Gremlin-enabled. This {@link GremlinPlugin} is not enabled
for the {@code ServiceLoader}. It is designed to be instantiated manually and compliant {@link GremlinScriptEngine}
instances will automatically install it by default when created.

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