Update get_current_hosts_in_room docstring to mention partial state

Signed-off-by: Sean Quah <[email protected]>

Author: Sean Quah

synapse/storage/databases/main/roommember.py

@@ -1029,6 +1029,14 @@ async def get_current_hosts_in_room(self, room_id: str) -> List[str]:
         longest is good because they're most likely to have anything we ask
         about.
 
+        Uses `m.room.member`s in the room state at the current forward extremities to
+        determine which hosts are in the room.
+
+        Will return inaccurate results for rooms with partial state, since the state for
+        the forward extremities of those rooms will exclude most members. We may also
+        calculate room state incorrectly for such rooms and believe that a host is or
+        is not in the room when the opposite is true.
+
         Returns:
             Returns a list of servers sorted by longest in the room first. (aka.
             sorted by join with the lowest depth first).