private final String untilString() {
        return null == this.untilTraversal ? "until(false)" : "until(" + this.untilTraversal + ')';
    }
@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/RepeatStep.java