ValueError: DATABASE_PUBLIC_URL environment variable is not set or is invalid

#parse the database url
DATABASE_URL = os.environ.get('DATABASE_PUBLIC_URL')
db_config = dj_database_url.parse(DATABASE_URL)

DATABASES = {
    "default": {
        #"ENGINE": "django.db.backends.sqlite3",
        #"NAME": BASE_DIR / "db.sqlite3",
        "ENGINE": 'django.db.backends.postgresql',
        "NAME": db_config['NAME'],
        "USER": db_config['USER'],
        "PASSWORD": db_config['PASSWORD'],
        "HOST": db_config['HOST'],
        "PORT": db_config['PORT'],
    }
}

#Secret key configuration
SECRET_KEY = SECRET_KEY

the following is my .env of course not using realdata
DB_PASSWORD_ME=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
DATABASE_PUBLIC_URL=postgresql://postgres:xxxxxxxxxxxxxxxxxx@xxxxxxxxxxxxx.proxy.rlwy.net:34833/railway
NAME=xxxxxxx
USER=postgres
PASSWORD=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
HOST=postgres.railway.internal
PORT=5432

#my secret key
SECRET_KEY=xxxxx-xxxxx-C(xxxxxx)xxxxxxxxxxxxxxxxxxxx

Thanks.... the attached file is the last log i have.