code: def _read_ssm_locs(in_file):
      
      out = {}
      with open(in_file) as in_handle:
          in_handle.readline()  # header
          for line in in_handle:
              sid, loc = line.split()[:2]
              chrom, pos = loc.split("_")
              out[sid] = (chrom, int(pos))
      return out
docs: Map SSMs to chromosomal locations.