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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def domain_name(self, levels=1):
 """ Produce an Internet domain name with the specified number of subdomain levels. nichols-phillips.com williamson-hopkins.jackson.com """

        if levels < 1:
            raise ValueError("levels must be greater than or equal to 1")
        if levels == 1:
            return self.domain_word() + '.' + self.tld()
        else:
            return self.domain_word() + '.' + self.domain_name(levels - 1)