public boolean parseBoolean(final GremlinParser.BooleanLiteralContext booleanLiteral) {
        return (boolean) visitBooleanLiteral(booleanLiteral);
    }
Parse a boolean literal context and return the boolean literal
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/language/grammar/GenericLiteralVisitor.java