<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def touch(fname):
 """ Mimics the `touch` command Busy loops until the mtime has actually been changed, use for tests only """

    orig_mtime = get_mtime(fname)
    while get_mtime(fname) == orig_mtime:
        pathlib.Path(fname).touch()