function isNative(value) {
      if (value == null) {
        return false;
      }
      if (toString.call(value) == funcClass) {
        return reNative.test(fnToString.call(value));
      }
      return (typeof value == 'object' &&
        (isHostObject(value) ? reNative : reHostCtor).test(value)) || false;
    }
Checks if `value` is a native function.

@static
@memberOf _
@category Lang
@param {*} value The value to check.
@returns {boolean} Returns `true` if `value` is a native function, else `false`.
@example

_.isNative(Array.prototype.push);
// => true

_.isNative(_);
// => false