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 classified as a `RegExp` object.

@static
@memberOf _
@since 0.1.0
@category Lang
@param {*} value The value to check.
@returns {boolean} Returns `true` if `value` is a regexp, else `false`.
@example

_.isRegExp(/abc/);
// => true

_.isRegExp('/abc/');
// => false