          for idx, frame in enumerate(tqdm(self.frames.file_list_sorted,
                                           desc="Saving extracted faces")):
              frame_name = frame["frame_fullname"]
  
              if not self.alignments.frame_exists(frame_name):
                  logger.verbose("Skipping '%s' - Alignments not found", frame_name)
                  continue
 
</s> remove 
        for frame in tqdm(self.frames.file_list_sorted, desc="Saving extracted faces"):
 </s> add         skip_num = self.arguments.extract_every_n
        if skip_num != 1:
            logger.info("Skipping every %s frames", skip_num)
        for idx, frame in enumerate(tqdm(self.frames.file_list_sorted,
                                         desc="Saving extracted faces")): </s> remove                     "for excluding low-res images from a training set." +
 </s> add                     "for excluding low-res images from a training set.. Can pass in the '-een' "
                    "(--extract-every-n) parameter to only extract every nth frame." + </s> remove                     "alignment data. This is a lot quicker than re-detecting faces." +
 </s> add                     "alignment data. This is a lot quicker than re-detecting faces. Can pass in "
                    "the '-een' (--extract-every-n) parameter to only extract every nth frame." +
            if idx % skip_num != 0:
                logger.trace("Skipping '%s' due to extract_every_n = %s", frame_name, skip_num)
                continue
          for idx, frame in enumerate(tqdm(self.frames.file_list_sorted,
                                           desc="Saving extracted faces")):
              frame_name = frame["frame_fullname"]
            if idx % skip_num != 0:
                logger.trace("Skipping '%s' due to extract_every_n = %s", frame_name, skip_num)
                continue
  
              if not self.alignments.frame_exists(frame_name):
                  logger.verbose("Skipping '%s' - Alignments not found", frame_name)
                  continue
keep keep add keep keep keep keep
 Add "extract-every-n" option to alignments tool 
tools/lib_alignments/jobs.py