Mongodb / mongo-php-library array_key_exists() usage

In the PHP library the following files use the deprecated array_key_exists()

./src/Model/IndexInfoIteratorIterator.php
./src/Model/IndexInfo.php
./src/Model/DatabaseInfo.php
./src/Model/CollectionInfo.php
./src/Operation/BulkWrite.php
./tests/Database/DatabaseFunctionalTest.php
./tests/Operation/ModifyCollectionFunctionalTest.php
./tests/Collection/CrudSpecFunctionalTest.php

Is this an update waiting due to its triviality or is there another reason?