Add remove_from_body to OpenAIHTTPBackend (#184)

This PR adds the `remove_from_body` parameter to `OpenAIHTTPBackend`,
which allows users to remove keys from the body of requests made to the
OpenAI server. This is needed for us to profile
[tokasaurus](https://github.com/ScalingIntelligence/tokasaurus), which
does not support the `max_completion_tokens` or `stream` parameters.

---------

Co-authored-by: Mark Kurtz <mark.j.kurtz@gmail.com>

Author: jackcook

src/guidellm/backend/openai.py

@@ -70,6 +70,14 @@ class OpenAIHTTPBackend(Backend):
         the values of these keys will be used as the parameters for the respective
         endpoint.
         If not provided, no extra query parameters are added.
+    :param extra_body: Body parameters to include in requests to the OpenAI server.
+        If "chat_completions", "models", or "text_completions" are included as keys,
+        the values of these keys will be included in the body for the respective
+        endpoint.
+        If not provided, no extra body parameters are added.
+    :param remove_from_body: Parameters that should be removed from the body of each
+        request.
+        If not provided, no parameters are removed from the body.
     """
 
     def __init__(
@@ -85,6 +93,7 @@ def __init__(
         max_output_tokens: Optional[int] = None,
         extra_query: Optional[dict] = None,
         extra_body: Optional[dict] = None,
+        remove_from_body: Optional[list[str]] = None,
     ):
         super().__init__(type_="openai_http")
         self._target = target or settings.openai.base_url
@@ -122,6 +131,7 @@ def __init__(
         )
         self.extra_query = extra_query
         self.extra_body = extra_body
+        self.remove_from_body = remove_from_body
         self._async_client: Optional[httpx.AsyncClient] = None
 
     @property
@@ -253,9 +263,8 @@ async def text_completions(  # type: ignore[override]
 
         headers = self._headers()
         params = self._params(TEXT_COMPLETIONS)
-        body = self._body(TEXT_COMPLETIONS)
         payload = self._completions_payload(
-            body=body,
+            endpoint_type=TEXT_COMPLETIONS,
             orig_kwargs=kwargs,
             max_output_tokens=output_token_count,
             prompt=prompt,
@@ -330,12 +339,11 @@ async def chat_completions(  # type: ignore[override]
         logger.debug("{} invocation with args: {}", self.__class__.__name__, locals())
         headers = self._headers()
         params = self._params(CHAT_COMPLETIONS)
-        body = self._body(CHAT_COMPLETIONS)
         messages = (
             content if raw_content else self._create_chat_messages(content=content)
         )
         payload = self._completions_payload(
-            body=body,
+            endpoint_type=CHAT_COMPLETIONS,
             orig_kwargs=kwargs,
             max_output_tokens=output_token_count,
             messages=messages,
@@ -411,7 +419,7 @@ def _params(self, endpoint_type: EndpointType) -> dict[str, str]:
 
         return self.extra_query
 
-    def _body(self, endpoint_type: EndpointType) -> dict[str, str]:
+    def _extra_body(self, endpoint_type: EndpointType) -> dict[str, Any]:
         if self.extra_body is None:
             return {}
 
@@ -426,12 +434,12 @@ def _body(self, endpoint_type: EndpointType) -> dict[str, str]:
 
     def _completions_payload(
         self,
-        body: Optional[dict],
+        endpoint_type: EndpointType,
         orig_kwargs: Optional[dict],
         max_output_tokens: Optional[int],
         **kwargs,
     ) -> dict:
-        payload = body or {}
+        payload = self._extra_body(endpoint_type)
         payload.update(orig_kwargs or {})
         payload.update(kwargs)
         payload["model"] = self.model
@@ -455,6 +463,10 @@ def _completions_payload(
                 payload["stop"] = None
                 payload["ignore_eos"] = True
 
+        if self.remove_from_body:
+            for key in self.remove_from_body:
+                payload.pop(key, None)
+
         return payload
 
     @staticmethod