'Update the result of a subtask with additional results.
Kwarg arguments are incremented to the existing values.
The exception is for `state`, which if specified is used to override the existing value.'

def increment(self, succeeded=0, failed=0, skipped=0, retried_nomax=0, retried_withmax=0, state=None):

    self.attempted += (succeeded + failed)
    self.succeeded += succeeded
    self.failed += failed
    self.skipped += skipped
    self.retried_nomax += retried_nomax
    self.retried_withmax += retried_withmax
    if (state is not None):
        self.state = state
