docs: def process_line(self, record):
          "Process a single record. This assumes only a single sample output."
          cleaned = []
  
          for key in self.vcf_fields:
              out = self.process_column(key, getattr(record, key))
              if isinstance(out, (list, tuple)):
                  cleaned.extend(out)
              else:
                  cleaned.append(out)
  
          for key in self.info_fields:
              out = self.process_column(key, record.INFO.get(key, None))
              if isinstance(out, (list, tuple)):
                  cleaned.extend(out)
              else:
                  cleaned.append(out)
  
          return cleaned