code: def attach_core_filters(cls):
          
          opts = cls._meta
          base_filters = cls.base_filters.copy()
          cls.base_filters.clear()
          for name, filter_ in six.iteritems(base_filters):
              if isinstance(filter_, AutoFilters):
                  field = filterset.get_model_field(opts.model, filter_.name)
                  filter_exclusion = filter_.extra.pop('drop', [])
                  for lookup_expr in utils.lookups_for_field(field):
                      if lookup_expr not in filter_exclusion:
                          new_filter = cls.filter_for_field(field, filter_.name, lookup_expr)
                          # by convention use field name for filters with exact lookup_expr
                          if lookup_expr != 'exact':
                              filter_name = LOOKUP_SEP.join([name, lookup_expr])
                          else:
                              filter_name = name
                          cls.base_filters[filter_name] = new_filter
docs: Attach core filters to filterset