pycharm erroneously marks seemingy undefined variable as 'error' (unresolved reference), no error upon execution

Question

Pycharm (Pycharm 2022.3.3 Community Edition) shows an error (unresolved reference) in the code attached in the image. In the function "func_test1" the variable "a" seems to be ?shadowed? by the variable "a" of the object "obj". In the function "func_test2" there is no issue about the variable "anythingexcepta". Upon running the script, everything works just fine. The three prints are: 5, 12 and 22, just as expected (i am using python 3.9).

So my questions are:

1. Why does this error occur? Is it some kind of shadowing? (although the script runs just fine)
2. Why does it occur in "func_test1", but nor in "func_test2"?
3. Is the behaviour of pycharm intended behaviour, if yes, why?
4. Is there a way to get rid of this erroneous error, apart from naming the variable something else.

I made this test script to showcase the error, ran the script and it ran just fine. But i still have no idea, why the error shows in the first place.

here's the code of the test script:

class testClass:
    def __init__(self, a):
        self.a = a

def func_test1(a):
    def func_inner1(obj):
        obj.a += a
    return func_inner1

def func_test2(anythingexcepta):
    def func_inner2(obj):
        obj.a += anythingexcepta
    return func_inner2


obj = testClass(5)

func_1 = func_test1(7)
func_2 = func_test2(10)

print(obj.a)
func_1(obj)
print(obj.a)
func_2(obj)
print(obj.a)