Use stub file to keep class CommandGroup clean

nonebot/command/group.py

@@ -0,0 +1,26 @@
+from typing import Union, Callable
+
+from nonebot.command import on_command
+from nonebot.typing import CommandName_T
+
+
+class CommandGroup:
+    """
+    Group a set of commands with same name prefix.
+    """
+
+    __slots__ = ('basename', 'base_kwargs')
+
+    def __init__(self, name: Union[str, CommandName_T], **kwargs):
+        self.basename = (name,) if isinstance(name, str) else name
+        if 'aliases' in kwargs:
+            del kwargs['aliases']  # ensure there is no aliases here
+        self.base_kwargs = kwargs
+
+    def command(self, name: Union[str, CommandName_T], **kwargs) -> Callable:
+        sub_name = (name,) if isinstance(name, str) else name
+        name = self.basename + sub_name
+
+        final_kwargs = self.base_kwargs.copy()
+        final_kwargs.update(kwargs)
+        return on_command(name, **final_kwargs)