Support discovering gemini, anthropic, xai models by calling their /v1/model endpoint (#9530)

* fix: initial commit for adding provider model discovery to gemini

* feat(gemini/): add model discovery for gemini/ route

* docs(set_keys.md): update docs to show you can check available gemini models as well

* feat(anthropic/): add model discovery for anthropic api key

* feat(xai/): add model discovery for XAI

enables checking what models an xai key can call

* ci: bump ci config yml

* fix(topaz/common_utils.py): fix linting error

* fix: fix linting error for python38

litellm/llms/xai/common_utils.py

@@ -0,0 +1,51 @@
+from typing import Optional
+
+import httpx
+
+import litellm
+from litellm.llms.base_llm.base_utils import BaseLLMModelInfo
+from litellm.secret_managers.main import get_secret_str
+
+
+class XAIModelInfo(BaseLLMModelInfo):
+    @staticmethod
+    def get_api_base(api_base: Optional[str] = None) -> Optional[str]:
+        return api_base or get_secret_str("XAI_API_BASE") or "https://api.x.ai"
+
+    @staticmethod
+    def get_api_key(api_key: Optional[str] = None) -> Optional[str]:
+        return api_key or get_secret_str("XAI_API_KEY")
+
+    @staticmethod
+    def get_base_model(model: str) -> Optional[str]:
+        return model.replace("xai/", "")
+
+    def get_models(
+        self, api_key: Optional[str] = None, api_base: Optional[str] = None
+    ) -> list[str]:
+        api_base = self.get_api_base(api_base)
+        api_key = self.get_api_key(api_key)
+        if api_base is None or api_key is None:
+            raise ValueError(
+                "XAI_API_BASE or XAI_API_KEY is not set. Please set the environment variable, to query XAI's `/models` endpoint."
+            )
+        response = litellm.module_level_client.get(
+            url=f"{api_base}/v1/models",
+            headers={"Authorization": f"Bearer {api_key}"},
+        )
+
+        try:
+            response.raise_for_status()
+        except httpx.HTTPStatusError:
+            raise Exception(
+                f"Failed to fetch models from XAI. Status code: {response.status_code}, Response: {response.text}"
+            )
+
+        models = response.json()["data"]
+
+        litellm_model_names = []
+        for model in models:
+            stripped_model_name = model["id"]
+            litellm_model_name = "xai/" + stripped_model_name
+            litellm_model_names.append(litellm_model_name)
+        return litellm_model_names