* Layout#delete_cells with a list of cell object
* Layout#delete_cell_rec with a cell object
* Layout#prune_cell with a cell object
* Layout#prune_cells for pruning multiple cells in one call
* Layout#prune_subcells with a cell object
* Layout#prune_subcells with multiple root cells
* Layout#flatten with a cell object
* Layout#flatten_into with cell objects
* Layout#delete_cell with a cell object
* Default value "all" for "levels" argument in "prune_subcells" and "prune_cell"
* Default value "all" for "levels" and "true" for "prune" argument in "flatten"
* Default value "all" for "levels" and "unity" for "trans" argument in "flatten_into"