ModuleNotFoundError: No module named 'shareplum'

Question

I got below error nevertheless package itself has been installed and can be seen by doing pip list. What issue might it be?

Error:

Broken DAG: [/opt/airflow/dags/sharepoint_test.py] Traceback (most recent call last):
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/opt/airflow/dags/sharepoint_test.py", line 8, in <module>
    from shareplum import Site, Office365
ModuleNotFoundError: No module named 'shareplum'

Package is installed:

airflow@airflowhost:/opt/airflow$ pip list | grep Sha
SharePlum                                0.5.1

Code which throws error:

import csv
from airflow.models import DAG
from airflow.operators.python import PythonOperator
from airflow.utils.dates import days_ago
from shareplum import Site, Office365
from shareplum.site import Version
import json, os

USERNAME = ''
PASSWORD = ''
SHAREPOINT_URL = ''
SHAREPOINT_SITE = ''
SHAREPOINT_DOC = ''

class SharePoint:
    def auth(self):
        self.authcookie = Office365(SHAREPOINT_URL, username=USERNAME, password=PASSWORD).GetCookies()
        self.site = Site(SHAREPOINT_SITE, version=Version.v365, authcookie=self.authcookie)

        return self.site


    def connect_folder(self, folder_name):
        self.auth_site = self.auth()
        self.sharepoint_dir = '\\'.join([SHAREPOINT_DOC, folder_name])
        self.folder = self.auth_site.Folder(self.sharepoint_dir)
        return self.folder

    def download_file(self, file_name, folder_name):
        self._folder = self.connect_folder(folder_name)
        return self._folder.get_file(file_name)

def process_file():
    file_name = 'sample.pdf'
    folder_name = 'Reference'
    file  = SharePoint().download_file(file_name, folder_name)

with DAG("sharepoint_test",
         schedule_interval=None,
         start_date=days_ago(2)) as dag:

    process_file = PythonOperator(task_id="process-file",
                                  python_callable=process_file)

    process_file