chore(commons): tiny fixes of step type checking (#846)

Author: delatrie

allure-python-commons/src/_allure.py

@@ -1,5 +1,5 @@
 from functools import wraps
-from typing import Any, Callable, TypeVar, Union, overload
+from typing import Any, Callable, TypeVar, overload
 
 from allure_commons._core import plugin_manager
 from allure_commons.types import LabelType, LinkType, ParameterMode
@@ -162,14 +162,16 @@ def manual():
 
 
 @overload
-def step(title: str) -> "StepContext": ...
+def step(title: str) -> "StepContext":
+    ...
 
 
 @overload
-def step(title: _TFunc) -> _TFunc: ...
+def step(title: _TFunc) -> _TFunc:
+    ...
 
 
-def step(title: Union[str, _TFunc]) -> Union["StepContext", _TFunc]:
+def step(title):
     if callable(title):
         return StepContext(title.__name__, {})(title)
     else:
@@ -199,7 +201,7 @@ def impl(*a, **kw):
             with StepContext(self.title.format(*args, **params), params):
                 return func(*a, **kw)
 
-        return impl
+        return impl  # type: ignore
 
 
 class Attach: