fix exports (#366)

Author: Roger-luo

src/kirin/__init__.py

@@ -1,7 +1,5 @@
 # re-exports the public API of the kirin package
-from kirin import ir
-
-from . import types as types
+from . import ir as ir, types as types, lowering as lowering
 from .exception import enable_stracetrace, disable_stracetrace
 
-__all__ = ["ir", "types", "enable_stracetrace", "disable_stracetrace"]
+__all__ = ["ir", "types", "lowering", "enable_stracetrace", "disable_stracetrace"]

src/kirin/ir/traits/callable.py

@@ -20,7 +20,7 @@ class CallableStmtInterface(StmtTrait, ABC, Generic[StmtType]):
 
     @classmethod
     @abstractmethod
-    def get_callable_region(cls, stmt: "Statement") -> "Region":
+    def get_callable_region(cls, stmt: "StmtType") -> "Region":
         """Returns the body of the callable region"""
         ...