refactor(rpc_server): add type hints and docstrings for heartbeat and registry update methods

bec_widgets/utils/rpc_server.py

@@ -4,7 +4,7 @@ import functools
 import traceback
 import types
 from contextlib import contextmanager
-from typing import TYPE_CHECKING, TypeVar
+from typing import TYPE_CHECKING, Callable, TypeVar
 
 from bec_lib.client import BECClient
 from bec_lib.endpoints import MessageEndpoints
@@ -163,7 +163,11 @@ class RPCServer:
             return None
         return self._serialize_bec_connector(obj)
 
-    def emit_heartbeat(self):
+    def emit_heartbeat(self) -> None:
+        """
+        Emit a heartbeat message to the GUI server.
+        This method is called periodically to indicate that the server is still running.
+        """
         logger.trace(f"Emitting heartbeat for {self.gui_id}")
         try:
             self.client.connector.set(
@@ -174,7 +178,11 @@ class RPCServer:
         except RedisError as exc:
             logger.error(f"Error while emitting heartbeat: {exc}")
 
-    def broadcast_registry_update(self, connections: dict):
+    def broadcast_registry_update(self, connections: dict) -> None:
+        """
+        Broadcast the registry update to all the callbacks.
+        This method is called whenever the registry is updated.
+        """
         data = {}
         for key, val in connections.items():
             if not isinstance(val, BECConnector):
@@ -208,12 +216,11 @@ class RPCServer:
         }
 
     @staticmethod
-    def _get_becwidget_ancestor(widget):
+    def _get_becwidget_ancestor(widget) -> BECConnector | None:
         """
         Traverse up the parent chain to find the nearest BECConnector.
         Returns None if none is found.
         """
-        from bec_widgets.utils import BECConnector
 
         parent = widget.parent()
         while parent is not None:
@@ -223,7 +230,15 @@ class RPCServer:
         return None
 
     # Suppose clients register callbacks to receive updates
-    def add_registry_update_callback(self, cb):
+    def add_registry_update_callback(self, cb: Callable) -> None:
+        """
+        Add a callback to be called whenever the registry is updated.
+        The specified callback is called whenever the registry is updated.
+
+        Args:
+            cb (Callable): The callback to be added. It should accept a dictionary of all the
+            registered RPC objects as an argument.
+        """
         self._registry_update_callbacks.append(cb)
 
     def shutdown(self):  # TODO not sure if needed when cleanup is done at level of BECConnector