Further improve pydocs for warm_up

Author: vblagoje

haystack/tools/tool.py

@@ -103,7 +103,8 @@ def warm_up(self) -> None:
         Prepare the Tool for use.
 
         Override this method to establish connections to remote services, load models,
-        or perform other resource-intensive initialization.
+        or perform other resource-intensive initialization. This method should be idempotent,
+        as it may be called multiple times.
         """
         pass
 

haystack/tools/toolset.py

@@ -190,6 +190,7 @@ def warm_up(self) -> None:
         Prepare the Toolset for use.
 
         Override this method to set up shared resources like database connections or HTTP sessions.
+        This method should be idempotent, as it may be called multiple times.
         """
         pass