input: Write a python function to compute the timebase scaling given a preset list of timebases and a scaling factor.
  assert timebase_scaling(4) == 0.5
  assert timebase_scaling(7) == 0.3
  assert timebase_scaling(9) == 0.1
output: def timebase_scaling(scaling_factor):
      timebases = [1, 0.5, 0.3, 0.1]
      return timebases[scaling_factor - 6]