lib/classes/Variables.js/Variables/overwrite
class Variables:  overwrite(variableStringsString) {
    let finalValue;
    const variableStringsArray = variableStringsString.split(',');
    const allValuesFromSource = variableStringsArray
      .map(variableString => this.getValueFromSource(variableString));
    return BbPromise.all(allValuesFromSource).then(valuesFromSources => {
      valuesFromSources.find(valueFromSource => {
        finalValue = valueFromSource;
        return (finalValue !== null && typeof finalValue !== 'undefined') &&
          !(typeof finalValue === 'object' && _.isEmpty(finalValue));
      });
      return BbPromise.resolve(finalValue);
    });
  }