code: static String prefix(final Fastq fastq) {
          checkNotNull(fastq);
          Matcher m = PREFIX.matcher(fastq.getDescription());
          if (!m.matches()) {
              throw new PairedEndFastqReaderException("could not parse prefix from description " + fastq.getDescription());
          }
          return m.group(1);
      }
docs: Return the prefix of the paired end read name of the specified fastq.
  
  @param fastq fastq, must not be null
  @return the prefix of the paired end read name of the specified fastq