fixed pycharm type hint problem by using a `TypeVar` for the annotation of the decorated function

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = webutils-df
-version = 0.0.4
+version = 0.0.5
 author = Daniil F.
 author_email = mail@placeholder123.to
 description = Miscellaneous web utilities

src/webutils/util.py

@@ -2,7 +2,7 @@ import logging
 import asyncio
 from functools import wraps
 from inspect import signature
-from typing import Callable, Awaitable, Dict, Tuple, Any
+from typing import Callable, Awaitable, Dict, Tuple, Any, TypeVar
 
 from aiohttp.client import ClientSession
 
@@ -10,17 +10,16 @@ from aiohttp.client import ClientSession
 LOGGER_NAME = 'webutils'
 logger = logging.getLogger(LOGGER_NAME)
 
+AsyncFunction = TypeVar('AsyncFunction')
+
 
 def _get_param_idx_and_default(function: Callable, param_name: str) -> Tuple[int, Any]:
     params = signature(function).parameters
     return list(params.keys()).index(param_name), params[param_name].default
 
 
-# TODO: Figure out why PyCharm does not produce type hints to a function decorated in this manner,
-#       when using the decorator without parentheses (e.g. @in_async_session instead of @in_async_session()
-#       in this case), as soon as the `Callable` return type is added to that decorator's signature.
-def in_async_session(_func: Callable = None, *,
-                     session_kwargs: Dict[str, Any] = None, session_param_name: str = 'session'):
+def in_async_session(_func: AsyncFunction = None, *,
+                     session_kwargs: Dict[str, Any] = None, session_param_name: str = 'session') -> AsyncFunction:
     """
     Useful decorator for any async function that uses the `aiohttp.ClientSession` to make requests.
 
@@ -51,7 +50,7 @@ def in_async_session(_func: Callable = None, *,
     if session_kwargs is None:
         session_kwargs = {}
 
-    def decorator(function: Callable) -> Callable:
+    def decorator(function: AsyncFunction) -> AsyncFunction:
         # Using `functools.wraps` to preserve information about the actual function being decorated
         # More details: https://docs.python.org/3/library/functools.html#functools.wraps
         @wraps(function)