diff --git a/colossalai/inference/config.py b/colossalai/inference/config.py
index 9266e6927..c563aa138 100644
--- a/colossalai/inference/config.py
+++ b/colossalai/inference/config.py
@@ -1,9 +1,8 @@
 """
 Our config contains various options for inference optimization, it is a unified API that wraps all the configurations for inference.
 """
-import dataclasses
 import logging
-from dataclasses import dataclass
+from dataclasses import dataclass, fields
 from typing import Any, Dict, Optional, Union
 
 import torch
@@ -215,7 +214,7 @@ class InferenceConfig:
     @classmethod
     def from_dict(cls, config_dict: Dict[str, Any]) -> "InferenceConfig":
         # Get the list of attributes of this dataclass.
-        attrs = [attr.name for attr in dataclasses.fields(cls)]
+        attrs = [attr.name for attr in fields(cls)]
         inference_config_args = {}
         for attr in attrs:
             if attr in config_dict:
diff --git a/colossalai/inference/core/async_engine.py b/colossalai/inference/core/async_engine.py
index e23d0b90f..9c630177d 100644
--- a/colossalai/inference/core/async_engine.py
+++ b/colossalai/inference/core/async_engine.py
@@ -10,7 +10,7 @@ logging.basicConfig(level=logging.DEBUG, format="%(asctime)s - %(name)s - %(leve
 logger = logging.getLogger("colossalai-inference")
 
 
-def _raise_exception_on_finish(task: asyncio.Task, request_tracker: "RequestTracker") -> None:
+def _raise_exception_on_finish(task: asyncio.Task, request_tracker: "Tracer") -> None:
     msg = "Task finished unexpectedly. This should never happen! "
     try:
         try:
@@ -26,8 +26,14 @@ def _raise_exception_on_finish(task: asyncio.Task, request_tracker: "RequestTrac
 
 
 class RequstStream:
-    """A stream of Output for a request that can be
-    iterated over asynchronously."""
+    """
+    A stream of Output for a request that can be iterated over asynchronously.
+        Attributes: 1.request_id: The id of the request.
+                    2._future: A future that will be set when the request is finished.
+        Methods: set_result and get_result, results will be set when finished, for once, and
+        the `self.future` will be set to done.
+
+    """
 
     def __init__(self, request_id: int) -> None:
         self.request_id = request_id
@@ -51,6 +57,10 @@ class RequstStream:
 class Tracer:
     """
     Recording new requests and finished requests.
+        Attributes: 1._request_streams: We create one stream for each request to trace the output.
+                    2._finished_requests: A queue to store the finished requests.
+                    3._new_requests: New requests will be stored in this queue first, before sending them to the engine.
+                    4.new_requests_event: An event to notify the engine that there are new requests.
     """
 
     def __init__(self) -> None:
@@ -133,7 +143,8 @@ class Tracer:
 
 class _AsyncInferenceEngine(InferenceEngine):
     """
-    Async methods for Inference Engine.
+    Async methods for Inference Engine. This engine is an extension for InferenceEngine, and the additional methods will only be used for
+        Methods: 1. async_step: The async version of Engine.step()
     """
 
     async def async_step(self) -> List[str]: