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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 list(self, host_rec=None, service_rec=None, hostfilter=None):
 """ Returns a list of vulnerabilities based on t_hosts.id or t_services.id. If neither are set then statistical results are added :param host_rec: db.t_hosts.id :param service_rec: db.t_services.id :param hostfilter: Valid hostfilter or None """

        return self.send.vuln_list(host_rec, service_rec, hostfilter)