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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 authenticate_keystone_user(self, keystone, user, password, tenant):
 """Authenticates a regular user with the keystone public endpoint."""

        self.log.debug('Authenticating keystone user ({})...'.format(user))
        ep = keystone.service_catalog.url_for(service_type='identity',
                                              interface='publicURL')
        keystone_ip = urlparse.urlparse(ep).hostname

        return self.authenticate_keystone(keystone_ip, user, password,
                                          project_name=tenant)