code: def add_schema_attributes(container, nexson_version):
      
      if _is_by_id_hbf(nexson_version):
          _add_by_id_nexson_schema_attributes(container)
      elif _is_badgerfish_version(nexson_version):
          _add_badgerfish_nexson_schema_attributes(container)
      elif _is_direct_hbf(nexson_version):
          _add_direct_nexson_schema_attributes(container)
      else:
          raise NotImplementedError('unrecognized nexson variant {}'.format(nexson_version))
docs: Adds several attributes to `container`:
      _using_hbf_meta  - boolean. True for HoneyBadgerFish v1-style meta elements ('^prop': value
                  rather than 'meta': {'$':value})
      and the following _SchemaFragment instances:
      _NexmlEl_Schema