:rtype: list of Protection Domains

def protection_domains(self):
        """
        :rtype: list of Protection Domains
        """
        self.connection._check_login()
        response = self.connection._do_get("{}/{}".format(self.connection._api_url, "types/ProtectionDomain/instances")).json()
        all_pds = []
        for pd in response:
            all_pds.append(
                SIO_Protection_Domain.from_dict(pd)
            )
        return all_pds