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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def copytree_hardlink(source, dest):
 """ Recursively copy a directory ala shutils.copytree, but hardlink files instead of copying. Available on UNIX systems only. """

    copy2 = shutil.copy2
    try:
        shutil.copy2 = os.link
        shutil.copytree(source, dest)
    finally:
        shutil.copy2 = copy2