[commands] Stop yielding duplicate commands from walk_commands

discord/ext/commands/core.py

@@ -1136,8 +1136,12 @@ class GroupMixin:
         return command
 
     def walk_commands(self):
-        """An iterator that recursively walks through all commands and subcommands."""
+        """An iterator that recursively walks through all commands and subcommands.
-        for command in tuple(self.all_commands.values()):
+
+        .. versionchanged:: 1.4
+            Duplicates due to aliases are no longer returned
+        """
+        for command in self.commands:
             yield command
             if isinstance(command, GroupMixin):
                 yield from command.walk_commands()