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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 migratable_vc_domains(self):
 """ Gets the VC Migration Manager API client. Returns: MigratableVcDomains: """

        if not self.__migratable_vc_domains:
            self.__migratable_vc_domains = MigratableVcDomains(self.__connection)
        return self.__migratable_vc_domains