chore: enable pyupgrade fixes (#1806)

# What does this PR do?

The goal of this PR is code base modernization.

Schema reflection code needed a minor adjustment to handle UnionTypes
and collections.abc.AsyncIterator. (Both are preferred for latest Python
releases.)

Note to reviewers: almost all changes here are automatically generated
by pyupgrade. Some additional unused imports were cleaned up. The only
change worth of note can be found under `docs/openapi_generator` and
`llama_stack/strong_typing/schema.py` where reflection code was updated
to deal with "newer" types.

Signed-off-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>

llama_stack/providers/inline/agents/meta_reference/agent_instance.py

@@ -10,8 +10,8 @@ import re
 import secrets
 import string
 import uuid
+from collections.abc import AsyncGenerator
 from datetime import datetime, timezone
-from typing import AsyncGenerator, List, Optional, Union
 
 import httpx
 
@@ -112,7 +112,7 @@ class ChatAgent(ShieldRunnerMixin):
             output_shields=agent_config.output_shields,
         )
 
-    def turn_to_messages(self, turn: Turn) -> List[Message]:
+    def turn_to_messages(self, turn: Turn) -> list[Message]:
         messages = []
 
         # NOTE: if a toolcall response is in a step, we do not add it when processing the input messages
@@ -161,7 +161,7 @@ class ChatAgent(ShieldRunnerMixin):
     async def create_session(self, name: str) -> str:
         return await self.storage.create_session(name)
 
-    async def get_messages_from_turns(self, turns: List[Turn]) -> List[Message]:
+    async def get_messages_from_turns(self, turns: list[Turn]) -> list[Message]:
         messages = []
         if self.agent_config.instructions != "":
             messages.append(SystemMessage(content=self.agent_config.instructions))
@@ -201,8 +201,8 @@ class ChatAgent(ShieldRunnerMixin):
 
     async def _run_turn(
         self,
-        request: Union[AgentTurnCreateRequest, AgentTurnResumeRequest],
-        turn_id: Optional[str] = None,
+        request: AgentTurnCreateRequest | AgentTurnResumeRequest,
+        turn_id: str | None = None,
     ) -> AsyncGenerator:
         assert request.stream is True, "Non-streaming not supported"
 
@@ -321,10 +321,10 @@ class ChatAgent(ShieldRunnerMixin):
         self,
         session_id: str,
         turn_id: str,
-        input_messages: List[Message],
+        input_messages: list[Message],
         sampling_params: SamplingParams,
         stream: bool = False,
-        documents: Optional[List[Document]] = None,
+        documents: list[Document] | None = None,
     ) -> AsyncGenerator:
         # Doing async generators makes downstream code much simpler and everything amenable to
         # streaming. However, it also makes things complicated here because AsyncGenerators cannot
@@ -374,8 +374,8 @@ class ChatAgent(ShieldRunnerMixin):
     async def run_multiple_shields_wrapper(
         self,
         turn_id: str,
-        messages: List[Message],
-        shields: List[str],
+        messages: list[Message],
+        shields: list[str],
         touchpoint: str,
     ) -> AsyncGenerator:
         async with tracing.span("run_shields") as span:
@@ -443,10 +443,10 @@ class ChatAgent(ShieldRunnerMixin):
         self,
         session_id: str,
         turn_id: str,
-        input_messages: List[Message],
+        input_messages: list[Message],
         sampling_params: SamplingParams,
         stream: bool = False,
-        documents: Optional[List[Document]] = None,
+        documents: list[Document] | None = None,
     ) -> AsyncGenerator:
         # if document is passed in a turn, we parse the raw text of the document
         # and sent it as a user message
@@ -760,7 +760,7 @@ class ChatAgent(ShieldRunnerMixin):
 
     async def _initialize_tools(
         self,
-        toolgroups_for_turn: Optional[List[AgentToolGroup]] = None,
+        toolgroups_for_turn: list[AgentToolGroup] | None = None,
     ) -> None:
         toolgroup_to_args = {}
         for toolgroup in (self.agent_config.toolgroups or []) + (toolgroups_for_turn or []):
@@ -847,7 +847,7 @@ class ChatAgent(ShieldRunnerMixin):
             tool_name_to_args,
         )
 
-    def _parse_toolgroup_name(self, toolgroup_name_with_maybe_tool_name: str) -> tuple[str, Optional[str]]:
+    def _parse_toolgroup_name(self, toolgroup_name_with_maybe_tool_name: str) -> tuple[str, str | None]:
         """Parse a toolgroup name into its components.
 
         Args:
@@ -921,7 +921,7 @@ async def get_raw_document_text(document: Document) -> str:
 
 def _interpret_content_as_attachment(
     content: str,
-) -> Optional[Attachment]:
+) -> Attachment | None:
     match = re.search(TOOLS_ATTACHMENT_KEY_REGEX, content)
     if match:
         snippet = match.group(1)