Fixed namespace issues

Author: Lisio

src/Command.php

@@ -12,7 +12,7 @@
 use MongoDB\Driver\Exception\RuntimeException;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
-use MongoDB\Driver\Session;
+use MongoDB\Driver\Session as DriverSession;
 use MongoDB\Driver\WriteConcern;
 use MongoDB\Driver\WriteResult;
 use Yii;
@@ -87,7 +87,7 @@ class Command extends BaseObject
      */
     private $_readConcern;
     /**
-     * @var Session|null session to be used by this command
+     * @var DriverSession session to be used by this command
      */
     private $_session;
 
@@ -173,7 +173,7 @@ public function setReadConcern($readConcern)
 
     /**
      * Sets session for this command.
-     * @param Session $session session
+     * @param DriverSession $session session
      * @return $this self reference
      */
     public function setSession($session)

src/Connection.php

@@ -8,7 +8,6 @@
 namespace yii\mongodb;
 
 use MongoDB\Driver\Manager;
-use MongoDB\Driver\Session;
 use yii\base\Component;
 use yii\base\InvalidConfigException;
 use Yii;
@@ -183,7 +182,7 @@ class Connection extends Component
     private $_fileStreamWrapperRegistered = false;
 
     /**
-     * @var \MongoDB\Driver\Session|null session
+     * @var \MongoDB\Driver\Session session
      */
     private $_session;