I'm learning about Python decorators and would appreciate feedback on my implementation.

Here's my example code:

@timer
def slow_function():
    import time
    time.sleep(2)
    return "Done"

Specifically, I'd like to know:

1. Is this a correct usage of decorators?
2. What's missing from the implementation (I notice the @timer decorator itself isn't defined)
3. Best practices for implementing timing decorators

Thank you for your help!