input: Write a function to create a REST API in Python that allows deleting an item from a list. The function should return a JSON response with a message indicating whether the item was successfully deleted or not found. If the input item is not in the list, the response should indicate that the item was not found.
  
  assert delete_item("Banana")==json.dumps({"message": "Item successfully deleted."})
  assert delete_item("Grape")==json.dumps({"message": "Item not found."})
output: def delete_item(item):
      items = ["Apple", "Banana", "Cherry"]
      if item in items:
          items.remove(item)
          return json.dumps({"message": "Item successfully deleted."})
      else:
          return json.dumps({"message": "Item not found."})