Note that barcodes are not something this is a feature of a fasta or fastq record, but rather specific to a few applications (basically, barcoded sequencing run data). If we were instead loading a database of sequences (e.g., all of the protein sequences in the PDB, or all of the 16S sequence in Greengenes), this would always be ``None``, so it might make more sense to have as part of a subclass.