lint: tidy up code in cli module

app/cli/__init__.py

@@ -0,0 +1,22 @@
+import argparse
+from abc import abstractmethod
+from typing import TYPE_CHECKING, Any
+
+if TYPE_CHECKING:
+    _SubparserType = argparse._SubParsersAction[argparse.ArgumentParser]  # pylint: disable=protected-access
+else:
+    _SubparserType = Any
+
+
+class BaseCliHandler:
+    def __init__(self, args: argparse.Namespace) -> None:
+        self.args = args
+
+    @classmethod
+    @abstractmethod
+    def add_subparser_to(cls, subparsers: _SubparserType) -> None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def run(self) -> None:
+        raise NotImplementedError