input: From the task description and code provided, we need to ensure that the `delete_item` function only deletes an item from the list if it exists. If the item does not exist, it should return a message indicating that the item was not found.
  
  ### Question:
  Given the code structure of the `delete_item` function, what is the expected response when attempting to delete an item that does not exist or when the item is successfully deleted?
  
  ### Steps:
  1. **Identify the functionality**: The function aims to delete an item from the `items` list and provide appropriate feedback.
  2. **Expected output**: If the item exists in the list, it should be removed and the function should return a success message. If the item does not exist, it should return a message indicating that the item was not found.
  
  ### Justification:
  By analyzing the `items` list and the logic inside the `delete_item` function, we can determine the expected output based on whether the item exists or not. This ensures that the system's response is both accurate and informative.
output:     if item in items:
          items.remove(item)
          return f"Item '{item}' deleted successfully."
      else:
          return f"Item '{item}' not found."