ValueError: Client secrets must be for a web or installed app - Notion API to Google sheets

I'm running into this error no matter what I try. I am very much a newbie and just want to connect google sheets to notion. If anyone can help, I'd greatly appreciate it. I'll include the code below. Occluded data is occluded because duh. credentials.json is the google sheets account credentials key.

I've tried two different sources to combine something that works, the main one being this: https://github.com/aakashadesara/notion-google-sheets-sync, if it helps.

A million thanks to anyone who can help.

from __future__ import print_function
import os.path
from googleapiclient.discovery import build
import pickle
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request
from google.oauth2 import service_account
from notion.client import NotionClient
from google.oauth2.credentials import Credentials

SCOPES = ['https://www.googleapis.com/auth/spreadsheets']
SERVICE_ACCOUNT_FILE = 'credentials.json'

SAMPLE_SPREADSHEET_ID = 'OCCLUDED' 
SAMPLE_RANGE_NAME = 'OCCLUDED'
NOTION_V2_TOKEN = "OCCLUDED"


creds = None
creds = service_account.Credentials.from_service_account_file(
        SERVICE_ACCOUNT_FILE, scopes=SCOPES)


def get_sheet():
    """Shows basic usage of the Sheets API.
    Prints values from a sample spreadsheet.
    """
    creds = None
    if os.path.exists('token.pickle'):
        with open('token.pickle', 'rb') as token:
            creds = pickle.load(token)
    if not creds or not creds.valid:
        if creds and creds.expired and creds.refresh_token:
            creds.refresh(Request())
        else:
            flow = InstalledAppFlow.from_client_secrets_file(
                'credentials.json', SCOPES)
            creds = flow.run_local_server(port=0)
        with open('token.pickle', 'wb') as token:
            pickle.dump(creds, token)

    service = build('sheets', 'v4', credentials=creds)

    sheet = service.spreadsheets()
    result = sheet.values().get(spreadsheetId=SAMPLE_SPREADSHEET_ID,
                                range=SAMPLE_RANGE_NAME).execute()
    values = result.get('values', [])

    if not values:
        print('No data found.')
        return None
    else:
        print('%s rows found.' % len(values))
        return values

def get_prop_type(data):
    # todo parse data to support types

    return 'text'

def notion_update(data):
    client = NotionClient(token_v2=NOTION_V2_TOKEN)
    
    block = client.get_block(NOTION_PAGE_LINK)
    cv = block.collection
    rows = cv.get_rows()

    cv.clear_properties()
    for row in rows:
        row.remove()


    title = data[0][0]
    cv.set_property('title', title, slug=title, property_type='title')
    for i, prop in enumerate(data[0][1:]):
        prop_type = get_prop_type(data[1][1:][i]) if data[1] and data[1][1:] else 'text'
        cv.set_property(prop, prop, slug=prop, property_type=prop_type)

    for row in data[1:]:
        new_row = cv.add_row()
        for i, value in enumerate(row):
            prop = data[0][i]
            new_row.set_property(prop, value)

if __name__ == '__main__':
    data = get_sheet()
    notion_update(data)