Tighten type of import_string

Author: cburgdorf

eth/db/__init__.py

@@ -1,6 +1,7 @@
 import os
 from typing import (
     Any,
+    cast,
     Type
 )
 
@@ -20,7 +21,7 @@ def get_db_backend_class(import_path: str = None) -> Type[BaseAtomicDB]:
             'CHAIN_DB_BACKEND_CLASS',
             DEFAULT_DB_BACKEND,
         )
-    return import_string(import_path)
+    return cast(Type[BaseAtomicDB], import_string(import_path))
 
 
 def get_db_backend(import_path: str = None, **init_kwargs: Any) -> BaseAtomicDB:

eth/estimators/__init__.py

@@ -1,6 +1,7 @@
 import os
 from typing import (
     Callable,
+    cast,
 )
 
 from eth.rlp.transactions import (
@@ -19,4 +20,4 @@ def get_gas_estimator() -> Callable[[BaseState, BaseTransaction], int]:
         'GAS_ESTIMATOR_BACKEND_FUNC',
         'eth.estimators.gas.binary_gas_search_intrinsic_tolerance',
     )
-    return import_string(import_path)
+    return cast(Callable[[BaseState, BaseTransaction], int], import_string(import_path))

eth/utils/module_loading.py

@@ -1,13 +1,15 @@
 import operator
 from importlib import import_module
 
+from types import (
+    ModuleType,
+)
 from typing import (
-    Any,
     Tuple,
 )
 
 
-def import_string(dotted_path: str) -> Any:
+def import_string(dotted_path: str) -> ModuleType:
     """
     Source: django.utils.module_loading
     Import a dotted module path and return the attribute/class designated by the