In this example, a placeholder with a converter for an integer ID is added at the end of the URL. By adding int: before the placeholder variable (arena_id), the ID can be used to query the Arena model/database table using the get(id) method of session.query, which expects an integer. If the datatype converter is not specified in the placeholder, the arena_id variable will contain a string character and won't be used by the get(id) method:

@app.route('/nba/api/v0.1/arena/<int:arena_id>', methods=['GET'])
def get_arena(arena_id):
  arena = session.query(Arena).get(arena_id)

With the parameter datatype specified, the requested arena object is returned by the ORM query and can be processed for a response.