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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 scan_on_disk(node, env, path=()):
 """ Scans a directory for on-disk files and directories therein. Looking up the entries will add these to the in-memory Node tree representation of the file system, so all we have to do is just that and then call the in-memory scanning function. """

    try:
        flist = node.fs.listdir(node.get_abspath())
    except (IOError, OSError):
        return []
    e = node.Entry
    for f in  filter(do_not_scan, flist):
        # Add ./ to the beginning of the file name so if it begins with a
        # '#' we don't look it up relative to the top-level directory.
        e('./' + f)
    return scan_in_memory(node, env, path)