dash-labs: ModuleNotFoundError: No module named 'pages.'

When trying to run the demo code of Chapter08-MultiPageDashApp I am getting this error. This error however doesn’t generates if I include only histogram.py file in /pages folder. As I add other files like bar_charts.py this error appears.

Detail print out:

(base) c:\my_drive\python\dashboards\plotlydash\flaskdash1>python app.py
Traceback (most recent call last):
  File "app.py", line 6, in <module>
    app = dash.Dash(
  File "C:\Users\hp\anaconda3\lib\site-packages\dash\dash.py", line 420, in __init__
    plugin.plug(self)
  File "C:\Users\hp\anaconda3\lib\site-packages\dash_labs\plugins\pages.py", line 327, in plug
    _import_layouts_from_pages(pages_folder)
  File "C:\Users\hp\anaconda3\lib\site-packages\dash_labs\plugins\pages.py", line 301, in _import_layouts_from_pages
    page_module = importlib.import_module(f"pages.{page_filename}")
  File "C:\Users\hp\anaconda3\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 961, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 961, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 973, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'pages.'