code: def remove_root_objective_bank(self, alias=None, objective_bank_id=None):
          
          url_path = self._urls.roots(alias=alias)
          current_root_ids = self._get_request(url_path)['ids']
          modified_list = []
          for root_id in current_root_ids:
              if root_id != str(objective_bank_id):
                  modified_list.append(root_id)
          new_root_ids = {
              'ids': modified_list
          }
          return self._put_request(url_path, new_root_ids)
docs: Removes a root objective bank.
  
          arg:    objective_bank_id (osid.id.Id): the ``Id`` of an
                  objective bank
          raise:  NotFound - ``objective_bank_id`` is not a root
          raise:  NullArgument - ``objective_bank_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          *compliance: mandatory -- This method must be implemented.*