docs: def get_host_datastore_system(host_ref, hostname=None):
      '''
      Returns a host's datastore system
  
      host_ref
          Reference to the ESXi host
  
      hostname
          Name of the host. This argument is optional.
      '''
  
      if not hostname:
          hostname = get_managed_object_name(host_ref)
      service_instance = get_service_instance_from_managed_object(host_ref)
      traversal_spec = vmodl.query.PropertyCollector.TraversalSpec(
          path='configManager.datastoreSystem',
          type=vim.HostSystem,
          skip=False)
      objs = get_mors_with_properties(service_instance,
                                      vim.HostDatastoreSystem,
                                      property_list=['datastore'],
                                      container_ref=host_ref,
                                      traversal_spec=traversal_spec)
      if not objs:
          raise salt.exceptions.VMwareObjectRetrievalError(
              'Host\'s \'{0}\' datastore system was not retrieved'
              ''.format(hostname))
      log.trace('[%s] Retrieved datastore system', hostname)
      return objs[0]['object']