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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 replace_lines_in_files(search_string, replacement_line):
 """ Finds lines containing the search string and replaces the whole line with the specified replacement string. """



    # have the user select some files
    paths = _s.dialogs.MultipleFiles('DIS AND DAT|*.*')
    if paths == []: return

    for path in paths:
        _shutil.copy(path, path+".backup")
        lines = read_lines(path)
        for n in range(0,len(lines)):
            if lines[n].find(search_string) >= 0:
                print(lines[n])
                lines[n] = replacement_line.strip() + "\n"
        write_to_file(path, join(lines, ''))

    return