Как проверить наличие ключа в словаре на Python языке

dic = {"A":1, "B":2}

def dicMemberCheck(key, dicObj):
    if key in dicObj:
        print("Existing key")
    else:
        print("Not existing")
        
dicMemberCheck("A")
dicMemberCheck("C")

Existing key
Not existing

>>> import timeit
>>> timeit.timeit('"A" in dic', setup='dic = {"A":1, "B":2}',number=1000000)
0.053480884567733256
>>> timeit.timeit('"A" in dic.keys()', setup='dic = {"A":1, "B":2}',number=1000000)
0.21542178873681905