code: def _get_reference_position(isomir):
      
      mut = isomir.split(":")[1]
      if mut == "0":
          return mut
      nt, pos = _parse_mut(mut)
      trim5 = isomir.split(":")[-2]
      off = -1 * len(trim5)
      if trim5.islower():
          off = len(trim5)
      if trim5 == "NA" or trim5 == "0":
          off = 0
      # print(isomir)
      # print([mut, pos, off, nt])
      return "%s%s" % (pos + off, nt)
docs: Liftover from isomir to reference mature