def METHOD_NAME(self):
    """
    Init self.exponent
    :return:
    """
    while True:
        self.exponent = random.randint(2, self.mod_base)
        if gcd(self.exponent, self.mod_base - 1) == 1:
            self.exponent_inverse = invert(self.exponent, self.mod_base - 1)
            break