@pimms.param<EOL><INDENT>def delete(d):<DEDENT>
if d in (True, False, Ellipsis): return d<EOL>else: raise ValueError('<STR_LIT>')<EOL>
pseudo_dir.delete is True if the pseudo_dir self-deletes on Python exit and False otherwise;
if this is Ellipsis, then self-deletes only when the cache-directory is created by the
PseudoDir class and is a temporary directory (i.e., not explicitly provided).