Python ограничить тип параметра функции

def add(a:int, b:int, c:int=0) -> int:
    """ Add 2 or 3 integers and return an integer result.
    """
    for var in [a, b, c]:        
        if not isinstance(var, int) :
            raise TypeError('Please make sure all inputs are integers')
    result = a + b + c
    return result
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