'Returns the event for the given class index.
This is the reverse process of the self.events_to_label method.
Args:
class_index: An integer in the range [0, self.num_classes).
events: A list-like sequence of events. This object is not used in this
implementation.
Returns:
An PianorollSequence event value.'

def class_index_to_event(self, class_index, events):

    assert (class_index < self.num_classes)
    event = []
    for i in range(self.input_size):
        if (class_index % 2):
            event.append(i)
        class_index >>= 1
    assert (class_index == 0)
    return tuple(event)
