code: def _special_dbkey_maps(dbkey, ref_file):
      
      remaps = {"hg19": "GRCh37",
                "hg38-noalt": "hg38"}
      if dbkey in remaps:
          base_dir = os.path.normpath(os.path.join(os.path.dirname(ref_file), os.pardir))
          vep_dir = os.path.normpath(os.path.join(base_dir, "vep"))
          other_dir = os.path.relpath(os.path.normpath(os.path.join(base_dir, os.pardir, remaps[dbkey], "vep")),
                                      base_dir)
          if os.path.exists(os.path.join(base_dir, other_dir)):
              if not os.path.lexists(vep_dir):
                  os.symlink(other_dir, vep_dir)
              return vep_dir
          else:
              return None
      else:
          return None
docs: Avoid duplicate VEP information for databases with chromosome differences like hg19/GRCh37.