什么是基于 PBT 的接口测试？看了下公开课

照抄了下不能运行（url 有更改）
File "E:\interface\ui_standard\utils\other_tool\apistar_util.py", line 9, in
import apistar
File "E:\interface\ui_standard\venv\lib\site-packages\apistar_init.py", line 11, in
from apistar.core import docs, validate
File "E:\interface\ui_standard\venv\lib\site-packages\apistar\core.py", line 7, in
from apistar.schemas.autodetermine import AUTO_DETERMINE
File "E:\interface\ui_standard\venv\lib\site-packages\apistar\schemas__init_.py", line 1, in
from apistar.schemas.openapi import OpenAPI
File "E:\interface\ui_standard\venv\lib\site-packages\apistar\schemas\openapi.py", line 6, in
from apistar.schemas.jsonschema import JSON_SCHEMA
File "E:\interface\ui_standard\venv\lib\site-packages\apistar\schemas\jsonschema.py", line 3, in
definitions = typesystem.SchemaDefinitions()
AttributeError: module 'typesystem' has no attribute 'SchemaDefinitions'