fix: resolve Python 3.9 compatibility and lint issues

- Replace 'str | None' syntax with 'Optional[str]' for Python 3.9 compatibility
- Fix import sorting in both _client.py and cog.py
- Remove unused 'cast' import from _client.py

Co-authored-by: Zeke Sikelianos <zeke@users.noreply.github.com>

Author: claude[bot]

src/replicate/_client.py

@@ -6,15 +6,14 @@
 from typing import (
     TYPE_CHECKING,
     Any,
-    Union,
-    Literal,
-    Mapping,
-    TypeVar,
+    AsyncIterator,
     Callable,
     Iterator,
+    Literal,
+    Mapping,
     Optional,
-    AsyncIterator,
-    cast,
+    TypeVar,
+    Union,
     overload,
 )
 from typing_extensions import Self, Unpack, ParamSpec, override

src/replicate/lib/cog.py

@@ -1,21 +1,21 @@
 """Integration with cog's current_scope functionality."""
 
-import os
 import logging
-from typing import Iterator, Any, cast
+import os
+from typing import Any, Iterator, Optional, cast
 
 logger = logging.getLogger("replicate")
 
 
-def get_api_token_from_current_scope() -> str | None:
+def get_api_token_from_current_scope() -> Optional[str]:
     """Get API token from cog's current_scope if available, otherwise return None.
     
     This function attempts to retrieve the API token from cog's current_scope context.
     It gracefully handles all errors and returns None if cog is not available or if
     any part of the retrieval process fails.
     
     Returns:
-        str | None: The API token from cog's current_scope, or None if not available.
+        Optional[str]: The API token from cog's current_scope, or None if not available.
     """
     try:
         import cog  # type: ignore[import-untyped, import-not-found]
@@ -47,7 +47,7 @@ def get_api_token_from_current_scope() -> str | None:
     return None
 
 
-def get_api_token_from_environment() -> str | None:
+def get_api_token_from_environment() -> Optional[str]:
     """Get API token from cog current scope if available, otherwise from environment."""
     # Try to get token from cog's current_scope first
     token = get_api_token_from_current_scope()