Explicit str type checking in model parsers

See comment here for context: #611 (comment)

Separating this diff from #611 to make it easier and get that one unblocked

extensions/HuggingFace/python/src/aiconfig_extension_hugging_face/local_inference/text_generation.py

@@ -129,9 +129,10 @@ def construct_stream_output(
         )
     accumulated_message = ""
     for new_text in streamer:
-        accumulated_message += new_text
-        options.stream_callback(new_text, accumulated_message, 0)
-        output.data = accumulated_message
+        if isinstance(new_text, str):
+            accumulated_message += new_text
+            options.stream_callback(new_text, accumulated_message, 0)
+            output.data = accumulated_message
     return output
 
 

extensions/LLama-Guard/python/python/src/aiconfig_extension_llama_guard/LLamaGuard.py

@@ -245,10 +245,15 @@ async def run_inference(
         output_text = self.tokenizer.decode(
             response[0][prompt_len:], skip_special_tokens=True
         )
+        output_data_content: str = ''
+        if isinstance(output_text, str):
+            output_data_content = output_text
+        else:
+            raise ValueError(f"Output {output_text} needs to be of type 'str' but is of type: {type(output_text)}")
         output = ExecuteResult(
             **{
                 "output_type": "execute_result",
-                "data": output_text,
+                "data": output_data_content,
                 "execution_count": 0,
                 "metadata": {},
             }

extensions/llama/python/llama.py

@@ -87,9 +87,15 @@ async def _run_inference_helper(self, model_input, options) -> List[Output]:
                 if options:
                     options.stream_callback(data, acc, index)
             print(flush=True)
+
+            output_data_value: str = ''
+            if isinstance(acc, str):
+                output_data_value = acc
+            else:
+                raise ValueError(f"Output {acc} needs to be of type 'str' but is of type: {type(acc)}")
             return ExecuteResult(
                 output_type="execute_result",
-                data=acc,
+                data=output_data_value,
                 metadata={}
             )
         else: