fix: add missing parameters order, limit, before, and after in get_assistants method for openai (#7537)

- Ensured that `before` and `after` parameters are only passed when provided to avoid AttributeError.
- Implemented safe access using default values for `before` and `after` to prevent missing attribute issues.
- Added consistent handling of `order` and `limit` to improve flexibility and robustness in API calls.

litellm/llms/openai/openai.py

@@ -1928,6 +1928,10 @@ class OpenAIAssistantsAPI(BaseLLM):
         max_retries: Optional[int],
         organization: Optional[str],
         client: Optional[AsyncOpenAI],
+        order: Optional[str] = 'desc',
+        limit: Optional[int] = 20,
+        before: Optional[str] = None,
+        after: Optional[str] = None,
     ) -> AsyncCursorPage[Assistant]:
         openai_client = self.async_get_openai_client(
             api_key=api_key,
@@ -1937,8 +1941,16 @@ class OpenAIAssistantsAPI(BaseLLM):
             organization=organization,
             client=client,
         )
-
-        response = await openai_client.beta.assistants.list()
+        request_params = {
+            "order": order,
+            "limit": limit,
+        }
+        if before:
+            request_params["before"] = before
+        if after:
+            request_params["after"] = after
+            
+        response = await openai_client.beta.assistants.list(**request_params)
 
         return response
 
@@ -1953,7 +1965,11 @@ class OpenAIAssistantsAPI(BaseLLM):
         max_retries: Optional[int],
         organization: Optional[str],
         client: Optional[AsyncOpenAI],
-        aget_assistants: Literal[True], 
+        aget_assistants: Literal[True],
+        order: Optional[str] = 'desc',
+        limit: Optional[int] = 20,
+        before: Optional[str] = None,
+        after: Optional[str] = None,
     ) -> Coroutine[None, None, AsyncCursorPage[Assistant]]:
         ...
 
@@ -1966,7 +1982,11 @@ class OpenAIAssistantsAPI(BaseLLM):
         max_retries: Optional[int],
         organization: Optional[str],
         client: Optional[OpenAI],
-        aget_assistants: Optional[Literal[False]], 
+        aget_assistants: Optional[Literal[False]],
+        order: Optional[str] = 'desc',
+        limit: Optional[int] = 20,
+        before: Optional[str] = None,
+        after: Optional[str] = None,
     ) -> SyncCursorPage[Assistant]: 
         ...
 
@@ -1981,6 +2001,10 @@ class OpenAIAssistantsAPI(BaseLLM):
         organization: Optional[str],
         client=None,
         aget_assistants=None,
+        order: Optional[str] = 'desc',
+        limit: Optional[int] = 20,
+        before: Optional[str] = None,
+        after: Optional[str] = None,
     ):
         if aget_assistants is not None and aget_assistants is True:
             return self.async_get_assistants(
@@ -1990,6 +2014,10 @@ class OpenAIAssistantsAPI(BaseLLM):
                 max_retries=max_retries,
                 organization=organization,
                 client=client,
+                order=order,
+                limit=limit,
+                before=before,
+                after=after,
             )
         openai_client = self.get_openai_client(
             api_key=api_key,
@@ -2000,7 +2028,18 @@ class OpenAIAssistantsAPI(BaseLLM):
             client=client,
         )
 
-        response = openai_client.beta.assistants.list()
+        request_params = {
+            "order": order,
+            "limit": limit,
+        }
+
+        if before:
+            request_params["before"] = before
+        if after:
+            request_params["after"] = after
+
+
+        response = openai_client.beta.assistants.list(**request_params)
 
         return response