Unsupported config option for services.volumes

volumes needs to be at the same indentation with services i.e

services:
    #...
volumes:
    db2_prod:

version: '3.7'
services:
    web:
        build: .
        command: python /code/manage.py runserver 0.0.0.0:8000
        volumes:
            - .:/code
        ports:
            - 8000:8000
        depends_on:
            - db
    db:
        image: postgres:11
        volumes:
            - postgres_data:/var/lib/postgresql/data/

volumes:
    postgres_data:

observe that version, services and volumes have same indent level. Moreover use spacebar for indentation, use of tab may create problem.