pomdp-py: ModuleNotFoundError: No module named 'pomdp_py.framework.basics'

I follow the install instruction and successfully install the package. But when I try to run the example, it gives the following error. No idea what happened.

python -m pomdp_problems.tiger.tiger_problem
Traceback (most recent call last):
  File "/Users/chenjie/opt/anaconda3/lib/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/Users/chenjie/opt/anaconda3/lib/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/Users/chenjie/opt/anaconda3/lib/python3.8/site-packages/pomdp_problems/tiger/tiger_problem.py", line 38, in <module>
    import pomdp_py
  File "/Users/chenjie/opt/anaconda3/lib/python3.8/site-packages/pomdp_py/__init__.py", line 4, in <module>
    from pomdp_py.framework.basics import *
ModuleNotFoundError: No module named 'pomdp_py.framework.basics'