Flask error - TypeError: объект 'NoneType' не может быть подписан

Question

Пожалуйста, я получаю две ошибки при запуске приложения. Это простое приложение, которое отображает данные из моей базы данных. Пожалуйста, помогите мне решить эту проблему.

См. Мой код ниже:

import pymongo
from flask import Flask
import datetime

app = Flask(__name__)
myClient = None
dataBase = None
nyColl = None

@app.route("/",methods=['GET'])
@app.route("/index",methods=['GET'])
def fetchData():
    #Connect to DB
    myclient = pymongo.MongoClient("mongodb+srv://")
    dataBase = myClient["pytest"]
    csvData = dataBase["csvcoll"]
    appLogs = dataBase["applogs"]
    #Log current time against each GET-request
    appLogs.insert_one({"type":"GET", "timestamp":datetime.datetime.now().strftime("%Y_%m_%d_%H_%M")})
    #Return all data
    retData = []
    for row in csvData.find():
        retData.append(row)
    return str(retData)

ОШИБКИ !!!

 in fetchData
    dataBase = myClient["pytest"]
    TypeError: 'NoneType' object is not subscriptable
    127.0.0.1 - - [04/May/2020 12:49:07] "GET / HTTP/1.1" 500 -

и

Traceback (most recent call last):
  File "/home/ubanna/.local/share/virtualenvs/Python_app-l0E1QI4C/lib/python3.8/site-packages/flask/app.py", line 2464, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/ubanna/.local/share/virtualenvs/Python_app -l0E1QI4C/lib/python3.8/site-packages/flask/app.py", line 2450, in wsgi_app
    response = self.handle_exception(e)
  File "/home/ubanna/.local/share/virtualenvs/Python_app-l0E1QI4C/lib/python3.8/site-packages/flask/app.py", line 1867, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/ubanna/.local/share/virtualenvs/Python_app-l0E1QI4C/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/ubanna/.local/share/virtualenvs/Python_app -l0E1QI4C/lib/python3.8/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/ubanna/.local/share/virtualenvs/Python_app -l0E1QI4C/lib/python3.8/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/ubanna/.local/share/virtualenvs/Python_app-l0E1QI4C/lib/python3.8/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/ubanna/.local/share/virtualenvs/Python_app-l0E1QI4C/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
    raise value