code: def walk(self):
          
          catalog = self.catalog
          query = self.additionalQuery.copy()
          query['portal_type'] = self.src_portal_type
          query['meta_type'] = self.src_meta_type
  
          if HAS_LINGUA_PLONE and 'Language' in catalog.indexes():
              query['Language'] = 'all'
  
          brains = catalog(query)
          limit = getattr(self, 'limit', False)
          if limit:
              brains = brains[:limit]
          obj_num_total = len(brains)
          logger.info('{} {} objects will be migrated walking through {}'
                      .format(obj_num_total, self.src_portal_type, catalog.id))
          counter = 0
          for brain in brains:
              if counter % 100 == 0:
                  logger.info('Progress: {} objects have been migrated out of {}'
                              .format(counter, obj_num_total))
              try:
                  obj = brain.getObject()
              except AttributeError:
                  LOG.error("Couldn't access %s" % brain.getPath())
                  continue
  
              if self.callBefore is not None and callable(self.callBefore):
                  if not self.callBefore(obj, **self.kwargs):
                      continue
  
              try:
                  state = obj._p_changed
              except Exception:
                  state = 0
              if obj is not None:
                  yield obj
                  # safe my butt
                  if state is None:
                      obj._p_deactivate()
              counter += 1
              if obj_num_total == counter:
                  logger.info(
                      'Progress: {} objects have been migrated out of {}'
                      .format(counter, obj_num_total))
docs: Walks around and returns all objects which needs migration
          It does exactly the same as the original method, but add some
          progress loggers.
  
          :return: objects (with acquisition wrapper) that needs migration
          :rtype: generator