Error: Could not locate a Flask application. Use the 'flask --app' option, 'FLASK_APP' environment variable, or a 'wsgi.py' or 'app.py' file in the current directory.

Usage: flask [OPTIONS] COMMAND [ARGS]...

  A general utility script for Flask applications.

  An application to load must be given with the '--app' option, 'FLASK_APP'
  environment variable, or with a 'wsgi.py' or 'app.py' file in the current
  directory.

Options:
  -e, --env-file FILE   Load environment variables from this file, taking
                        precedence over those set by '.env' and '.flaskenv'.
                        Variables set directly in the environment take highest
                        precedence. python-dotenv must be installed.
  -A, --app IMPORT      The Flask application or factory function to load, in
                        the form 'module:name'. Module can be a dotted import
                        or file path. Name is not required if it is 'app',
                        'application', 'create_app', or 'make_app', and can be
                        'name(args)' to pass arguments.
  --debug / --no-debug  Set debug mode.
  --version             Show the Flask version.
  --help                Show this message and exit.

Commands:
  routes  Show the routes for the app.
  run     Run a development server.
  shell   Run a shell in the app context.