Fix list_topics crash on Telethon 1.42

main.py

@@ -42,8 +42,61 @@
     TextWithEntities,
 )
 import re
+import struct
 from functools import wraps
 import telethon.errors.rpcerrorlist
+from telethon.tl.tlobject import TLRequest, TLObject
+
+
+class GetForumTopicsRequest(TLRequest):
+    """
+    Raw TL request for channels.getForumTopics.
+    Telethon 1.42 does not generate a wrapper for this method,
+    so we define it manually using the TL schema:
+    channels.getForumTopics#de560d1 flags:# channel:InputChannel
+        q:flags.0?string offset_date:int offset_id:int
+        offset_topic:int limit:int = messages.ForumTopics;
+    """
+    CONSTRUCTOR_ID = 0x0de560d1
+    SUBCLASS_OF_ID = 0x0
+
+    def __init__(self, channel, offset_date, offset_id, offset_topic, limit, q=None):
+        self.channel = channel
+        self.q = q
+        self.offset_date = offset_date
+        self.offset_id = offset_id
+        self.offset_topic = offset_topic
+        self.limit = limit
+
+    async def resolve(self, client, utils):
+        self.channel = utils.get_input_channel(await client.get_input_entity(self.channel))
+
+    def _bytes(self):
+        flags = 0
+        if self.q is not None:
+            flags |= 1
+        return b''.join((
+            struct.pack('<I', self.CONSTRUCTOR_ID),
+            struct.pack('<I', flags),
+            self.channel._bytes(),
+            TLObject.serialize_bytes(self.q) if self.q is not None else b'',
+            struct.pack('<i', self.offset_date),
+            struct.pack('<i', self.offset_id),
+            struct.pack('<i', self.offset_topic),
+            struct.pack('<i', self.limit),
+        ))
+
+    @classmethod
+    def from_reader(cls, reader):
+        flags = reader.read_int()
+        channel = reader.tgread_object()
+        q = reader.tgread_string() if flags & 1 else None
+        offset_date = reader.read_int()
+        offset_id = reader.read_int()
+        offset_topic = reader.read_int()
+        limit = reader.read_int()
+        return cls(channel=channel, offset_date=offset_date, offset_id=offset_id,
+                   offset_topic=offset_topic, limit=limit, q=q)
 
 
 class ValidationError(Exception):
@@ -1212,7 +1265,7 @@ async def list_topics(
             return "The specified supergroup does not have forum topics enabled."
 
         result = await client(
-            functions.channels.GetForumTopicsRequest(
+            GetForumTopicsRequest(
                 channel=entity,
                 offset_date=0,
                 offset_id=0,