Fixing linter issues

Author: apetenchea

arangoasync/connection.py

@@ -163,8 +163,10 @@ async def send_request(self, request: Request) -> Response:
         ):
             request.data = self._compression.compress(request.data)
             request.headers["content-encoding"] = self._compression.content_encoding()
-        if self._compression.accept_encoding() is not None:
-            request.headers["accept-encoding"] = self._compression.accept_encoding()
+
+        accept_encoding: str | None = self._compression.accept_encoding()
+        if accept_encoding is not None:
+            request.headers["accept-encoding"] = accept_encoding
 
         if self._auth:
             request.auth = self._auth