function hasCustomToString(obj) {
  return isFunction(obj.toString) && obj.toString !== 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);
   };

   // E.g.
   function getResult(fn, input) {
     return (fn || angular.identity)(input);
   };

   getResult(function(n) { return n * 2; }, 21);   // returns 42
   getResult(null, 21);                            // returns 21
   getResult(undefined, 21);                       // returns 21
   ```

@param {*} value to be returned.
@returns {*} the value passed in.