public function sumAccounts($user_id)
{
$mongodb = Connections::get('default')->connection;
$account = Accounts::connection()->connection->command(array('aggregate' => 'accounts', 'pipeline' => array(array('$project' => array('_id' => 0, 'amount' => '$amount', 'user_id' => '$user_id', 'username' => '$username')), array('$match' => array('user_id' => $user_id)), array('$group' => array('_id' => array('user_id' => '$user_id', 'username' => '$username'), 'amount' => array('$sum' => '$amount'))))));
return compact('account');
}
