Python Lambda Function as Callback: Example with LED Duty Cycle

This line of code defines a lambda function called 'callback' in Python. The lambda function takes an argument 't' and calls the 'duty()' method of an object 'self.led' with an argument of 500.

The lambda function can be used as a callback function in an event-driven programming paradigm. When the event occurs, the lambda function will be executed and the 'duty()' method of 'self.led' will be called with a duty cycle of 500.