lib/classes/Variables.js/Variables/getValueFromDeep
class Variables:  getValueFromDeep(variableString) {
    const deepPrefixReplace = RegExp(/(?:^deep:)\d+\.?/g);
    const variable = this.getVariableFromDeep(variableString);
    const deepRef = variableString.replace(deepPrefixReplace, '');
    let ret = this.populateValue(variable);
    if (deepRef.length) {
      // if there is a deep reference remaining
      ret = ret.then(result => {
        if (_.isString(result) && result.match(this.variableSyntax)) {
          const deepVariable = this.makeDeepVariable(result);
          return BbPromise.resolve(this.appendDeepVariable(deepVariable, deepRef));
        }
        return this.getDeeperValue(deepRef.split('.'), result);
      });
    }
    return ret;
  }