def add_progress(self, delta, done=None):
if done is not None:<EOL><INDENT>self.done = done<EOL><DEDENT>self.bar.current = max(min(self.done, self.current + delta), <NUM_LIT:0>)<EOL>self.rate_display.set_text(self.rate_text)<EOL>self.remaining_time_display.set_text(self.remaining_time_text)<EOL>return self.current == self.done<EOL>
Add to the current progress amount

        Add `delta` to the current progress amount. This also updates
        :attr:`rate` and :attr:`remaining_time`.

        The :attr:`current` progress is never less than 0 or greater
        than :attr:`done`.

        :param delta: amount to add, may be negative
        :param done: new value to use for done