Add much more detailed set_update_handler docstring

pyrogram/client/client.py

@@ -371,10 +371,41 @@ class Client:
     def set_update_handler(self, callback: callable):
         """Use this method to set the update handler.
 
+        You must call this method *before* you *start()* the Client.
+
         Args:
             callback (:obj:`callable`):
-                A function that takes "client, update, users, chats" as positional arguments.
+                A function that will be called when a new update is received from the server. It takes
-                It will be called when a new update is received from the server.
+                :obj:`(client, update, users, chats)` as positional arguments (Look at the section below for
+                a detailed description).
+
+        Other Parameters:
+            client (:obj:`pyrogram.Client`):
+                The Client itself, useful when you want to call other API methods inside the update handler.
+
+            update (:obj:`types.Update <pyrogram.api.types.Update>`):
+                The received update, which can be one of the many single Updates listed in the *updates*
+                field you see in the :obj:`types.Update <pyrogram.api.types.Update>` type.
+
+            users (:obj:`dict`):
+                Dictionary of all :obj:`types.User <pyrogram.api.types.User>` mentioned in the update.
+                You can access extra info about the user (such as *first_name*, *last_name*, etc...) by using
+                the IDs you find in the *update* argument (e.g.: *users[1768841572]*).
+
+            chats (:obj:`dict`):
+                Dictionary of all :obj:`types.Chat <pyrogram.api.types.Chat>` and
+                :obj:`types.Channel <pyrogram.api.types.Channel>` mentioned in the update.
+                You can access extra info about the chat (such as *title*, *participants_count*, etc...)
+                by using the IDs you find in the *update* argument (e.g.: *chats[1701277281]*).
+
+        Note:
+            The following Empty or Forbidden types may exist inside the *users* and *chats* dictionaries.
+            They mean you have been blocked by the user or banned from the group/channel.
+
+            - :obj:`types.UserEmpty <pyrogram.api.types.UserEmpty>`
+            - :obj:`types.ChatEmpty <pyrogram.api.types.ChatEmpty>`
+            - :obj:`types.ChatForbidden <pyrogram.api.types.ChatForbidden>`
+            - :obj:`types.ChannelForbidden <pyrogram.api.types.ChannelForbidden>`
         """
         self.update_handler = callback