[engine/tests/test_rest_api.py] Fix pylint warnings (#9199)

cvat/apps/engine/tests/test_rest_api.py

@@ -23,6 +23,7 @@
 from io import BytesIO, IOBase
 from itertools import product
 from time import sleep
+from typing import BinaryIO
 from unittest import mock
 
 import av
@@ -1768,13 +1769,13 @@ def get_status(self):
             def create_file(cls, key, _bytes):
                 cls._files[key] = _bytes
 
-            def get_file_status(self, key):
+            def get_file_status(self, key: str, /):
                 return Status.AVAILABLE if key in self._files else Status.NOT_FOUND
 
-            def _download_range_of_bytes(self, key, stop_byte, start_byte):
+            def _download_range_of_bytes(self, key: str, /, *, stop_byte: int, start_byte: int):
                 return self._files[key][start_byte:stop_byte]
 
-            def _download_fileobj_to_stream(self, key, stream):
+            def _download_fileobj_to_stream(self, key: str, stream: BinaryIO, /):
                 stream.write(self._files[key])
 
         cls.mock_aws = MockAWS