(#100) Missing permissions error in Facebook API clarification

problem description:

• we are getting (#100) Missing permissions errors while extracting facebook account ads
  insights data using programmatically generated access tokens using Graph API in python.
• later we generated access tokens in the app with ads_read and insights_read permission and we can able to extract the data successfully.

questions:

1.how can we generate access tokens with permissions programmatically using Graph API in python?
2.which token is advisable to extract data for ad account insights?

error message:
{
      "error": {
        "message": "(#100) Missing permissions",
        "type": "OAuthException",
        "code": 100,
        "fbtrace_id": "A4vPClDlI__dFmxxhiVVGRG"
      }
    }

access token generation code sample:

import requests

def get_fb_token(app_id, app_secret):
    url = 'https://graph.facebook.com/oauth/access_token'
    payload = {
        'grant_type': 'client_credentials',
        'client_id': app_id,
        'client_secret': app_secret
    }
    response = requests.post(url, params=payload)
    return response.json()['access_token']


app_id = 'XXXXXXXXXXXXXXX'
app_secret = 'XXXXXXXXXXXXXXXXX'

data_request = get_fb_token(app_id, app_secret)
print(data_request)

Note:

• we have also tried passing scope:ads_read, but we are getting the same error.
• we have also tried Facebook -SDK package, but we are getting the same access tokens.