请编写一个函数，它接受一个整数，然后返回一个该整数的平方。
def square_num(num):
    """
    Square the provided number.
    """
    # TODO: calculate the square of 'num' and return the result
    return num

print(square_num(5))
def square_num(num):
    """
    Square the provided number.
    """
    return num ** 2

print(square_num(5)) # 输出 25