def get_zoom_levels(process_zoom_levels=None, init_zoom_levels=None):
process_zoom_levels = _validate_zooms(process_zoom_levels)<EOL>if init_zoom_levels is None:<EOL><INDENT>return process_zoom_levels<EOL><DEDENT>else:<EOL><INDENT>init_zoom_levels = _validate_zooms(init_zoom_levels)<EOL>if not set(init_zoom_levels).issubset(set(process_zoom_levels)):<EOL><INDENT>raise MapcheteConfigError(<EOL>"<STR_LIT>")<EOL><DEDENT>return init_zoom_levels<EOL><DEDENT>
Validate and return zoom levels.