No module named 'bark.core'

[drxlchan]

I just install bark-ml as pypi. And when I tried the example. The error I got is
Traceback (most recent call last):
File "test.py", line 6, in
import bark_ml.environments.gym
File "/home/ubuntu/data/anacond3/envs/bark/lib/python3.7/site-packages/bark_ml/environments/init.py", line 1, in
from bark_ml.environments.single_agent_runtime import SingleAgentRuntime # pylint: disable=unused-import
File "/home/ubuntu/data/anacond3/envs/bark/lib/python3.7/site-packages/bark_ml/environments/single_agent_runtime.py", line 8, in
from bark.runtime.runtime import Runtime
File "/home/ubuntu/data/Jeffrey/bark/bark/runtime/init.py", line 1, in
from .runtime import Runtime
File "/home/ubuntu/data/Jeffrey/bark/bark/runtime/runtime.py", line 14, in
from bark.core.world.opendrive import *
ModuleNotFoundError: No module named 'bark.core'

I run it in a virtual anaconda environment under Linux. The version of python is 3.7.