public Builder beforeEval(final Consumer<Bindings> beforeEval) {
                this.beforeEval = beforeEval;
                return this;
            }
Specifies the function to execute prior to the script being evaluated.  This function can also be
specified globally on {@link GremlinExecutor.Builder#beforeEval(Consumer)}.
gremlin-groovy/src/main/java/org/apache/tinkerpop/gremlin/groovy/engine/GremlinExecutor.java