code: public FastaRecord<S> take() {
          RawFastaRecord rawRecord = takeRawRecord();
  
          // On EOF
          if (rawRecord == null)
              return null;
  
          return new FastaRecord<>(id++, rawRecord.description,
                  alphabet.parse(rawRecord.sequence));
      }
docs: Return next FASTA record or {@literal null} if end of stream is reached.
  
  <p>This method is thread-safe.</p>
  
  @return next FASTA record or {@literal null} if end of stream is reached