addOperatorDecorator (decoratorOrName, cb) {
    let decorator
    if (decoratorOrName instanceof OperatorDecorator) {
      decorator = decoratorOrName
    } else {
      decorator = new OperatorDecorator(decoratorOrName, cb)
    }
    debug('operatorMap::addOperatorDecorator', { name: decorator.name })
    this.decorators.set(decorator.name, decorator)
  }
Add a custom operator decorator
@param {string}   decoratorOrName - decorator identifier within the condition; i.e. instead of 'everyFact', 'someValue', etc
@param {function(factValue, jsonValue, next)} callback - the method to execute when the decorator is encountered.