private Object getSingleGenericLiteralArgument(final ParseTree ctx) {;
        final int childIndexOfParameterValue = ctx.getChildCount() == 6 ? 4 : 2;

        return antlr.argumentVisitor.visitGenericArgument(
                ParseTreeContextCastHelper.castChildToGenericLiteral(ctx, childIndexOfParameterValue));
    }
Get 1 generic literal argument from the antlr parse tree context, where the arguments have the child index
of 2 with the short form and 4 on the long form (e.g. eq(1) vs P.eq(1) respectively)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/language/grammar/TraversalPredicateVisitor.java