def checkGeneChangeAccrossAll(genecn, thresh=0.2):
  """
  used to find poor quality genes in CN data (works with multiple sample file)

  compute given a df of gene x sample CN counts, how much change there is accross samples for
  a same gene and returns ones that are below the threshold

  Args:
  -----
    genecn: gene cn data frame
    thresh: threshold in logfold change accross all of them
  """
  return genecn.columns[genecn.var()<thresh].tolist()