Unable to connect to Xero API using Python & OAuth 2

I'm trying to connect to a demo company using the Xero API in python. I want to setup a connection. I'm using the below code:

import os
from functools import wraps
from io import BytesIO
from logging.config import dictConfig

from flask import Flask, url_for, render_template, session, redirect, json, send_file
from flask_oauthlib.contrib.client import OAuth, OAuth2Application
from flask_session import Session
from xero_python.accounting import AccountingApi, ContactPerson, Contact, Contacts
from xero_python.api_client import ApiClient, serialize
from xero_python.api_client.configuration import Configuration
from xero_python.api_client.oauth2 import OAuth2Token
from xero_python.exceptions import AccountingBadRequestException
from xero_python.identity import IdentityApi
from xero_python.utils import getvalue

import logging_settings
from utils import jsonify, serialize_model

dictConfig(logging_settings.default_settings)

# configure main flask application
app = Flask(__name__)
app.config.from_object("default_settings")
app.config.from_pyfile("config.py", silent=True)

if app.config["ENV"] != "production":
    # allow oauth2 loop to run over http (used for local testing only)
    os.environ["OAUTHLIB_INSECURE_TRANSPORT"] = "1"

# configure persistent session cache
Session(app)
# configure flask-oauthlib application
# TODO fetch config from https://identity.xero.com/.well-known/openid-configuration #1
oauth = OAuth(app)
xero = oauth.remote_app(
    name="xero",
    version="2",
    client_id=app.config["CLIENT_ID"],
    client_secret=app.config["CLIENT_SECRET"],
    endpoint_url="https://api.xero.com/",
    authorization_url="https://login.xero.com/identity/connect/authorize",
    access_token_url="https://identity.xero.com/connect/token",
    refresh_token_url="https://identity.xero.com/connect/token",
    scope="offline_access openid profile email accounting.transactions "
    "accounting.reports.read accounting.journals.read accounting.settings "
    "accounting.contacts accounting.attachments assets projects",
)  # type: OAuth2Application


# configure xero-python sdk client
api_client = ApiClient(
    Configuration(
        debug=app.config["DEBUG"],
        oauth2_token=OAuth2Token(
            client_id=app.config["CLIENT_ID"], client_secret=app.config["CLIENT_SECRET"]
        ),
    ),
    pool_threads=1,
)

I have created the config.py file with my "Client_ID" & "Client_Secret" but I keep getting the below traceback:

line 41, in client_id=app.config["CLIENT_ID"], KeyError: 'CLIENT_ID

What am I doing wrong?