docs: def total_align_count(bam_filepath):
      '''Returns count of all mapped alignments in input BAM (based on index)'''
      count = 0
      for line in idxstats(bam_filepath):
          if line:
              chrom, _, mapped, unmapped = line.strip().split('\t')
              if chrom != '*':
                  count += int(mapped) + int(unmapped)
      return count