Add pipe docstring (#2868)

Co-authored-by: Chester Chen <[email protected]>

nvflare/fuel/utils/pipe/pipe.py

@@ -38,7 +38,7 @@ class Message:
     def __init__(self, msg_type: str, topic: str, data: Any, msg_id=None, req_id=None):
         check_str("msg_type", msg_type)
         if msg_type not in [Message.REPLY, Message.REQUEST]:
-            raise ValueError(f"invalid note_type '{msg_type}': must be one of {[Message.REPLY, Message.REQUEST]}")
+            raise ValueError(f"invalid msg_type '{msg_type}': must be one of {[Message.REPLY, Message.REQUEST]}")
         self.msg_type = msg_type
 
         check_str("topic", topic)
@@ -61,10 +61,46 @@ def __init__(self, msg_type: str, topic: str, data: Any, msg_id=None, req_id=Non
 
     @staticmethod
     def new_request(topic: str, data: Any, msg_id=None):
+        """Creates a new request message.
+
+        This static method creates a new `Message` object representing a request.
+
+        Args:
+            topic (str): The topic of the request message.
+                This is a string that identifies the subject or category of the request.
+            data (Any): The data associated with the request message.
+                This can be any type of data that is relevant to the request.
+            msg_id (Optional[Any]): An optional identifier for the message.
+                If provided, this ID is used to uniquely identify the message.
+                If not provided, a UUID will be generated to uniquely identify the message.
+
+        Returns:
+            Message: A `Message` object with the type set to `Message.REQUEST`,
+                and the provided `topic`, `data`, and `msg_id`.
+
+        """
         return Message(Message.REQUEST, topic, data, msg_id)
 
     @staticmethod
     def new_reply(topic: str, data: Any, req_msg_id, msg_id=None):
+        """Creates a new reply message in response to a request.
+
+        This static method creates a new `Message` object representing a reply to a previous request.
+
+        Args:
+            topic (str): The topic of the reply message.
+                This is a string that identifies the subject or category of the reply.
+            data (Any): The data associated with the reply message. This can be any type of data relevant to the reply.
+            req_msg_id (int): The identifier of the request message that this reply is responding to.
+                This ID links the reply to the original request.
+            msg_id (Optional[int]): An optional identifier for the reply message.
+                If provided, this ID is used to uniquely identify the message.
+                If not provided, a UUID will be generated to uniquely identify the message.
+
+        Returns:
+            Message: A `Message` object with the type set to `Message.REPLY`,
+                and the provided `topic`, `data`, `msg_id`, and `req_msg_id`.
+        """
         return Message(Message.REPLY, topic, data, msg_id, req_id=req_msg_id)
 
     def __str__(self):