old_contents: from flask import Flask
  
  # Create Flask application
  app = Flask(__name__)
  
  @app.route('/inventory')
  def index():
    """ Intro page of the inventory API
  
    This method will only return some welcome words.
  
    Returns:
      response: welcome words in json format and status 200
  
    Todo:
      * Finish the implementations.
      * Write the tests for this.
  
    """
    pass
  
  
  @app.route('/inventory/products/<int:id>', methods=['PUT'])
  def update_product(id):
    """ Update info about a product
  
    This method will update the info about a product
    (eg. amount of new, open box or used.)
  
    Args:
      id (string): The id of the product to be update
  
    Returns:
      response: update successful message with status 200 if succeeded
                or no product found with status 404 if cannot found the product
                or invalid update with status 400 if the update violates any limitation.
  
    Todo:
      * Finish the implementations.
      * Write the tests for this.
  
    """
    pass
  
new_contents: from flask import Flask
  
  # Create Flask application
  app = Flask(__name__)
  
  @app.route('/inventory')
  def index():
    """ Intro page of the inventory API
  
    This method will only return some welcome words.
  
    Returns:
      response: welcome words in json format and status 200
  
    Todo:
      * Finish the implementations.
      * Write the tests for this.
  
    """
    pass
  
  @app.route('/inventory/products', methods=['GET'])
  def get_product_list():
    """ Get info about all products
  
      This method will get the info about all the products
  
      Args:
        no arguments
  
      Returns:
        response: product information(product id, location id, used/new/open_box, total_quantity, restock_level)
        status 200 if succeeded
  
      Todo:
        * Finish the implementations.
        * Write the tests for this.
  
      """
  
  @app.route('/inventory/products/<int:id>', methods=['PUT'])
  def update_product(id):
    """ Update info about a product
  
    This method will update the info about a product
    (eg. amount of new, open box or used.)
  
    Args:
      id (string): The id of the product to be update
  
    Returns:
      response: update successful message with status 200 if succeeded
                or no product found with status 404 if cannot found the product
                or invalid update with status 400 if the update violates any limitation.
  
    Todo:
      * Finish the implementations.
      * Write the tests for this.
  
    """
    pass
  
subject: Create a GET products method