docs: def snpsift(self):
          """SnpSift"""
  
          tstart = datetime.now()
  
          # command = 'python %s/snpsift.py -i sanity_check/checked.vcf 2>log/snpsift.log' % (scripts_dir)
          # self.shell(command)
  
          ss = snpsift.SnpSift(self.vcf_file)
          ss.run()
  
          tend = datetime.now()
          execution_time = tend - tstart