optimize imports

remove extra idents
add check for dialog being a channel
using input_entity of dialogs

telethon/tl/custom/dialog.py

@@ -1,9 +1,6 @@
 from . import Draft
-from .. import TLObject, types
-from ..functions.channels import LeaveChannelRequest
-from ..functions.messages import DeleteHistoryRequest
+from .. import TLObject, types, functions
 from ... import utils
-from ...errors import PeerIdInvalidError
 
 
 class Dialog:
@@ -66,7 +63,6 @@ class Dialog:
         is_channel (`bool`):
             ``True`` if the `entity` is a :tl:`Channel`.
     """
-
     def __init__(self, client, dialog, entities, messages):
         # Both entities and messages being dicts {ID: item}
         self._client = client
@@ -101,11 +97,10 @@ class Dialog:
             self.input_entity, *args, **kwargs)
 
     async def delete(self):
-        try:
-            await self._client(DeleteHistoryRequest(self, 0))
-
-        except PeerIdInvalidError:
-            await self._client(LeaveChannelRequest(self))
+        if self.is_channel:
+            await self._client(functions.channels.LeaveChannelRequest(self.input_entity))
+        else:
+            await self._client(functions.messages.DeleteHistoryRequest(self.input_entity, 0))
 
     def to_dict(self):
         return {