code: def check_overlap(pos, ins, thresh):
      
      ins_pos = ins[0]
      ins_len = ins[2]
      ol = overlap(ins_pos, pos)
      feat_len = pos[1] - pos[0] + 1
  #    print float(ol) / float(feat_len)
      if float(ol) / float(feat_len) >= thresh:
          return True
      return False
docs: make sure thresh % feature is contained within insertion