diff --git a/parea/wrapper/openai.py b/parea/wrapper/openai.py
index fb50aba5..d5157923 100644
--- a/parea/wrapper/openai.py
+++ b/parea/wrapper/openai.py
@@ -8,7 +8,6 @@
 from ..utils.trace_utils import trace_data
 from .wrapper import Wrapper
 
-
 MODEL_COST_MAPPING: Dict[str, float] = {
     "gpt-4": 0.03,
     "gpt-4-0314": 0.03,
@@ -75,9 +74,7 @@ def resolver(trace_id: str, _args: Sequence[Any], kwargs: Dict[str, Any], respon
 
         model_rate = OpenAIWrapper.get_model_cost(model)
         model_completion_rate = OpenAIWrapper.get_model_cost(model, is_completion=True)
-        completion_cost = model_completion_rate * (
-            usage.get("completion_tokens", 0) / 1000
-        )
+        completion_cost = model_completion_rate * (usage.get("completion_tokens", 0) / 1000)
         prompt_cost = model_rate * (usage.get("prompt_tokens", 0) / 1000)
         total_cost = sum([prompt_cost, completion_cost])
 
@@ -119,12 +116,7 @@ def get_model_cost(model_name: str, is_completion: bool = False) -> float:
 
         cost = MODEL_COST_MAPPING.get(model_name, None)
         if cost is None:
-            msg = (
-                f"Unknown model: {model_name}. "
-                f"Please provide a valid OpenAI model name. "
-                f"Known models are: {', '.join(MODEL_COST_MAPPING.keys())}"
-            )
+            msg = f"Unknown model: {model_name}. " f"Please provide a valid OpenAI model name. " f"Known models are: {', '.join(MODEL_COST_MAPPING.keys())}"
             raise ValueError(msg)
 
         return cost
-