docs: def change(governor, freq=None):
      """
      change function
      """
      cpu_number = 0
  
      while True:
          try:
              subprocess.check_output([
                  "sudo", "bash", "-c",
                  "echo {governor} > {CPU_PREFIX}cpu{cpu_number}/cpufreq/scaling_governor"
                  .format(governor=governor,
                          CPU_PREFIX=CPU_PREFIX,
                          cpu_number=cpu_number)],
                                      stderr=subprocess.STDOUT)
          except:
              break
  
          if freq:
              subprocess.check_output([
                  "sudo", "bash", "-c",
                  "echo {freq} > {CPU_PREFIX}cpu{cpu_number}/cpufreq/scaling_setspeed"
                  .format(freq=freq,
                          CPU_PREFIX=CPU_PREFIX,
                          cpu_number=cpu_number)],
                                      stderr=subprocess.STDOUT)
  
          cpu_number += 1