def frequency=(freq)
      raise JSS::InvalidDataError, "New frequency must be one of :#{FREQUENCIES.keys.join ', :'}" unless FREQUENCIES.key?(freq)
      @frequency = FREQUENCIES[freq]
      @need_to_update = true
    end
def frequency=(freq)
      raise JSS::InvalidDataError, "New frequency must be one of :#{FREQUENCIES.keys.join ', :'}" unless FREQUENCIES.key?(freq)
      @frequency = FREQUENCIES[freq]
      @need_to_update = true
    end
Set a new frequency for this policy.

 @param freq[Symbol] the desired frequency, must be one of the keys of {FREQUENCIES}

 @return [void]