code: def get_tabix_cmd(config):
      
      try:
          bcftools = config_utils.get_program("bcftools", config)
          # bcftools has terrible error codes and stderr output, swallow those.
          bcftools_tabix = subprocess.check_output("{bcftools} 2>&1; echo $?".format(**locals()),
                                                   shell=True).decode().find("tabix") >= 0
      except config_utils.CmdNotFound:
          bcftools_tabix = False
      if bcftools_tabix:
          return "{0} tabix".format(bcftools)
      else:
          tabix = config_utils.get_program("tabix", config)
          return tabix
docs: Retrieve tabix command, handling new bcftools tabix and older tabix.