avoiding isFunction in _.include

underscore.js

@@ -172,7 +172,7 @@
 
   // Determine if a given value is included in the array or object using '==='.
   _.include = function(obj, target) {
-    if (obj && _.isFunction(obj.indexOf)) return _.indexOf(obj, target) != -1;
+    if (obj && obj.indexOf === nativeIndexOf) return obj.indexOf(target) != -1;
     return !! _.detect(obj, function(value) {
       return value === target;
     });