public Expression getExpression() {
            if (null == expression) {
                this.expression = new ExpressionBuilder(this.equation)
                        .variables(this.variables)
                        .implicitMultiplication(false)
                        .build();
            }
            return expression;
        }
A wrapper for the {@code Expression} class. That class is not marked {@code Serializable} and therefore gives
problems in OLAP specifically with Spark. This wrapper allows the {@code Expression} to be serialized in that
context with Java serialization.
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MathStep.java