docs: def pprint(sequence_file, annotation=None, annotation_file=None,
             block_length=10, blocks_per_line=6):
      """
      Pretty-print sequence(s) from a file.
      """
      annotations = []
  
      if annotation:
          annotations.append([(first - 1, last) for first, last in annotation])
  
      try:
          # Peek to see if this looks like a FASTA file.
          line = next(sequence_file)
          if line.startswith('>'):
              _pprint_fasta(itertools.chain([line], sequence_file),
                            annotations=annotations,
                            annotation_file=annotation_file,
                            block_length=block_length,
                            blocks_per_line=blocks_per_line)
          else:
              _pprint_line(line.strip(), annotations=annotations,
                           annotation_file=annotation_file,
                           block_length=block_length,
                           blocks_per_line=blocks_per_line)
      except StopIteration:
          pass