docs: def update_asset(self, asset_form=None):
          """Updates an existing asset.
  
          arg:    asset_form (osid.repository.AssetForm): the form
                  containing the elements to be updated
          raise:  IllegalState - ``asset_form`` already used in anupdate
                  transaction
          raise:  InvalidArgument - the form contains an invalid value
          raise:  NullArgument - ``asset_form`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          raise:  Unsupported - ``asset_form`` did not originate from
                  ``get_asset_form_for_update()``
          *compliance: mandatory -- This method must be implemented.*
  
          """
          return Asset(self._provider_session.update_asset(asset_form), self._config_map)