Fix files param in http client

Signed-off-by: Kirill Sosnovskikh <k.sosnovskikh@yadro.com>

src/frostfs_testlib/http/http_client.py

@@ -2,7 +2,7 @@ import io
 import json
 import logging
 import logging.config
-from typing import IO
+from typing import Mapping, Sequence
 
 import httpx
 
@@ -84,13 +84,20 @@ class HttpClient:
         return request_body
 
     @classmethod
-    def _parse_files(cls, files: dict | None) -> str | None:
+    def _parse_files(cls, files: Mapping | Sequence | None) -> str | None:
         if not files:
             return None
 
         filepaths = {}
 
-        for name, file in files.items():
+        if isinstance(files, Sequence):
+            items = files
+        elif isinstance(files, Mapping):
+            items = files.items()
+        else:
+            raise TypeError(f"'files' must be either Sequence or Mapping, got: {type(files).__name__}")
+
+        for name, file in items:
             if isinstance(file, io.IOBase):
                 filepaths[name] = file.name