def _filter_subtiles(self, subtiles, all_subtiles):
    '\n        Return an iterator with all sub tiles.\n        Yields (None, None, None) for non-intersecting tiles,\n        otherwise (subtile, subtile_bbox, intersection).\n        '
    for subtile in subtiles:
        if (subtile is None):
            (yield (None, None, None))
        else:
            sub_bbox = self.grid.meta_tile(subtile).bbox
            if all_subtiles:
                intersection = CONTAINS
            else:
                intersection = self.task.intersects(sub_bbox)
            if intersection:
                (yield (subtile, sub_bbox, intersection))
            else:
                (yield (None, None, None))
Return an iterator with all sub tiles.
Yields (None, None, None) for non-intersecting tiles,
otherwise (subtile, subtile_bbox, intersection).
def _filter_subtiles(self, subtiles, all_subtiles):
    '\n        Return an iterator with all sub tiles.\n        Yields (None, None, None) for non-intersecting tiles,\n        otherwise (subtile, subtile_bbox, intersection).\n        '
    for subtile in subtiles:
        if (subtile is None):
            (yield (None, None, None))
        else:
            sub_bbox = self.grid.meta_tile(subtile).bbox
            if all_subtiles:
                intersection = CONTAINS
            else:
                intersection = self.task.intersects(sub_bbox)
            if intersection:
                (yield (subtile, sub_bbox, intersection))
            else:
                (yield (None, None, None))