function isPlainObject(value) {
  if (!isObjectLike(value) || baseGetTag(value) != objectTag) {
    return false;
  }

  var proto = getPrototype(value);

  if (proto === null) {
    return true;
  }

  var Ctor = hasOwnProperty.call(proto, 'constructor') && proto.constructor;
  return typeof Ctor == 'function' && Ctor instanceof Ctor && funcToString.call(Ctor) == objectCtorString;
}
Checks if `value` is a plain object, that is, an object created by the
`Object` constructor or one with a `[[Prototype]]` of `null`.

@static
@memberOf _
@since 0.8.0
@category Lang
@param {*} value The value to check.
@returns {boolean} Returns `true` if `value` is a plain object, else `false`.
@example

function Foo() {
  this.a = 1;
}

_.isPlainObject(new Foo);
// => false

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

_.isPlainObject({ 'x': 0, 'y': 0 });
// => true

_.isPlainObject(Object.create(null));
// => true