docs: def _pprint_fasta(fasta, annotations=None, annotation_file=None,
                    block_length=10, blocks_per_line=6):
      """
      Pretty-print each record in the FASTA file.
      """
      annotations = annotations or []
  
      # Annotations by chromosome.
      as_by_chrom = collections.defaultdict(lambda: [a for a in annotations] or [])
      if annotation_file:
          for chrom, chrom_iter in _bed_iter(annotation_file):
              as_by_chrom[chrom].append(list(chrom_iter))
  
      for header, sequence in _fasta_iter(fasta):
          print(header)
          print(pprint_sequence(sequence,
                                annotations=as_by_chrom[header.split()[0]],
                                block_length=block_length,
                                blocks_per_line=blocks_per_line,
                                format=AnsiFormat))