/**
  * Get the query builder of the 'friend' model
  *
  * @return \Illuminate\Database\Eloquent\Builder
  */
 private function getMutualFriendsQueryBuilder(Model $other)
 {
     $user1['friendships'] = $this->findFriendships(Status::ACCEPTED)->get(['sender_id', 'recipient_id']);
     $user1['recipients'] = $user1['friendships']->pluck('recipient_id')->all();
     $user1['senders'] = $user1['friendships']->pluck('sender_id')->all();
     $user2['friendships'] = $other->findFriendships(Status::ACCEPTED)->get(['sender_id', 'recipient_id']);
     $user2['recipients'] = $user2['friendships']->pluck('recipient_id')->all();
     $user2['senders'] = $user2['friendships']->pluck('sender_id')->all();
     $mutualFriendships = array_unique(array_intersect(array_merge($user1['recipients'], $user1['senders']), array_merge($user2['recipients'], $user2['senders'])));
     return $this->whereNotIn('id', [$this->getKey(), $other->getKey()])->whereIn('id', $mutualFriendships);
 }