def delete_lower(script, layer_num=None):
if layer_num is None:<EOL><INDENT>layer_num = script.current_layer()<EOL><DEDENT>if layer_num != <NUM_LIT:0>:<EOL><INDENT>change(script, <NUM_LIT:0>)<EOL><DEDENT>for i in range(layer_num):<EOL><INDENT>delete(script, <NUM_LIT:0>)<EOL><DEDENT>return None<EOL>
Delete all layers below the specified one.

    Useful for MeshLab ver 2016.12, whcih will only output layer 0.