code: def upload_cart(cart, collection):
      
      cart_cols = cart_db()
  
      cart_json = read_json_document(cart.cart_file())
      try:
          cart_id = cart_cols[collection].save(cart_json)
      except MongoErrors.AutoReconnect:
          raise JuicerConfigError("Error saving cart to `cart_host`. Ensure that this node is the master.")
      return cart_id
docs: Connect to mongo and store your cart in the specified collection.