docs: def parent_organisations(self):
          '''The organisations this RTC belongs to.'''
          class ParentOrg:
              def __init__(self, sdo_id, org_id):
                  self.sdo_id = sdo_id
                  self.org_id = org_id
  
          with self._mutex:
              if not self._parent_orgs:
                  for sdo in self._obj.get_organizations():
                      if not sdo:
                          continue
                      owner = sdo.get_owner()
                      if owner:
                          sdo_id = owner._narrow(SDOPackage.SDO).get_sdo_id()
                      else:
                          sdo_id = ''
                      org_id = sdo.get_organization_id()
                      self._parent_orgs.append(ParentOrg(sdo_id, org_id))
          return self._parent_orgs