code: def _add_filters(self, **filters):
          
          for key, value in filters.items():
              if self._field_is_pk(key):
                  pk = self.cls.get_field('pk').normalize(value)
                  self._lazy_collection['pks'].add(pk)
              else:
                  # store the info to call the index later, in ``_prepare_sets``
                  # (to avoid doing extra work if the collection is never called)
                  index, suffix, extra_field_parts = self._parse_filter_key(key)
                  parsed_filter = ParsedFilter(index, suffix, extra_field_parts, value)
                  self._lazy_collection['sets'].append(parsed_filter)
  
          return self
docs: Define self._lazy_collection according to filters.