code: def set_pwm_frequency(self, value):
          
          self.__check_range('pwm_frequency', value)
          reg_val = self.calc_pre_scale(value)
          logger.debug("Calculated prescale value is %s" % reg_val)
          self.sleep()
          self.write(Registers.PRE_SCALE, reg_val)
          self.wake()
docs: Set the frequency for all PWM output
  
          :param value: the frequency in Hz