code: def _is_umi_consensus_bam(in_file):
      
      cmd = "samtools view -h %s | head -500000 | samtools view -c -f 1024"
      count = subprocess.check_output(cmd % in_file, shell=True)
      return int(count) == 0
docs: Check if input BAM file generated by fgbio consensus calls on UMIs.
  
      Identify these by lack of duplicated reads.
      This is useful for pre-aligned consensus BAMs feeding into octopus.