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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 increase_verbosity():
 """ Increase the verbosity of the root handler by one defined level. Understands custom logging levels like defined by my ``verboselogs`` module. """

    defined_levels = sorted(set(find_defined_levels().values()))
    current_index = defined_levels.index(get_level())
    selected_index = max(0, current_index - 1)
    set_level(defined_levels[selected_index])