TypeError: can't concat str to bytes

[xulifan]

Here is the simple code when running with python 3.8:

response1 = bts_client.list_instances()
for instance in response1.instances:
    response2 = bts_client.list_tables(instance.name)
    for table in response2.tables:
        print(instance.name, table.name)

Here is the error message:
File "/usr/local/lib/python3.8/site-packages/baidubce/services/bts/bts_client.py", line 205, in list_tables
path = bts.URL_PREFIX + b"/" + instance_name + b"/tables"
TypeError: can't concat str to bytes