fix(main.py): support cost calculation for text completion streaming object

litellm/utils.py

@@ -558,6 +558,13 @@ class TextChoices(OpenAIObject):
     def __setitem__(self, key, value):
         # Allow dictionary-style assignment of attributes
         setattr(self, key, value)
+    
+    def json(self, **kwargs):
+        try:
+            return self.model_dump()  # noqa
+        except:
+            # if using pydantic v1
+            return self.dict()
 
 
 class TextCompletionResponse(OpenAIObject):