code: def _get_pct(isomirs, mirna):
      
      pass_pos = []
      for isomir in isomirs.iterrows():
          mir = isomir[1]["chrom"]
          mut = isomir[1]["sv"]
          mut_counts = isomir[1]["counts"]
          total = mirna.loc[mir, "counts"] * 1.0 - mut_counts
          mut_diff = isomir[1]["diff"]
          ratio = mut_counts / total
          if mut_counts > 10 and ratio  > 0.4 and mut != "0" and mut_diff > 1:
              isomir[1]["ratio"] = ratio
              pass_pos.append(isomir[1])
      return pass_pos
docs: Get pct of variants respect to the reference
      using reads and different sequences