isPlainObject = function(value) {
      if (!(value && toString.call(value) == objectClass)) {
        return false;
      }
      var valueOf = value.valueOf,
          objProto = typeof valueOf == 'function' && (objProto = getPrototypeOf(valueOf)) && getPrototypeOf(objProto);

      return objProto
        ? (value == objProto || getPrototypeOf(value) == objProto)
        : shimIsPlainObject(value);
    }
Checks if `value` is an object created by the `Object` constructor.

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

function Stooge(name, age) {
  this.name = name;
  this.age = age;
}

_.isPlainObject(new Stooge('moe', 40));
// => false

_.isPlainObject([1, 2, 3]);
// => false

_.isPlainObject({ 'name': 'moe', 'age': 40 });
// => true