code: function pick(propName, propValue) {
  	var possibleClassIds = Object.keys(storage[propName] || {}).filter(function (classId) {
  		return (0, _lodash2.default)(storage[propName][classId], propValue);
  	});
  
  	return possibleClassIds.length > 0 ? parseInt(possibleClassIds[0], 10) : null;
  }
docs: get the classId