# File lib/monkey.rb, line 26
  def self.show_invisibles!(show = true)
    return @show_invisibles = show unless block_given?
    # actually, that is not thread-safe. but that's no issue, as
    # it is quite unlikely and does not cause any harm.
    show_invisibles_was, @show_invisibles = @show_invisibles, show
    result = yield
    @show_invisibles = show_invisibles_was
    result
  end