function hasCustomToString(obj) {
  return isFunction(obj.toString) && obj.toString !== Object.prototype.toString;
}
@ngdoc function
@name angular.identity
@module ng
@kind function

@description
A function that returns its first argument. This function is useful when writing code in the
functional style.

   ```js
     function transformer(transformationFn, value) {
       return (transformationFn || angular.identity)(value);
     };
   ```
@param {*} value to be returned.
@returns {*} the value passed in.