code: def get_object_keys(self, wfi_role=None):
          
          if self.object_key:
              return [self.object_key]
          if self.object_query_code:
              model = model_registry.get_model(self.object_type)
              return [m.key for m in
                      self.get_model_objects(model, wfi_role, **self.get_object_query_dict())]
docs: returns object keys according to task definition
          which can be explicitly selected one object (self.object_key) or
          result of a queryset filter.
  
          Returns:
              list of object keys