code: def _mark_dirty(self, xblock, value):
          
          # pylint: disable=protected-access
  
          # Deep copy the value being marked as dirty, so that there
          # is a baseline to check against when saving later
          if self not in xblock._dirty_fields:
              xblock._dirty_fields[self] = copy.deepcopy(value)
docs: Set this field to dirty on the xblock.