def walk(self):
    assert (self.handle_stale or self.handle_uncached)
    bbox = self.task.coverage.extent.bbox_for(self.tile_mgr.grid.srs)
    if self.seed_progress.already_processed():
        self.seed_progress.step_forward()
    else:
        try:
            self._walk(bbox, self.task.levels)
        except StopProcess:
            pass
    self.report_progress(self.task.levels[0], self.task.coverage.bbox)
def walk(self):
    assert (self.handle_stale or self.handle_uncached)
    bbox = self.task.coverage.extent.bbox_for(self.tile_mgr.grid.srs)
    if self.seed_progress.already_processed():
        self.seed_progress.step_forward()
    else:
        try:
            self._walk(bbox, self.task.levels)
        except StopProcess:
            pass
    self.report_progress(self.task.levels[0], self.task.coverage.bbox)