code: public static String getWthInsiCode(Map wthData) {
          String wst_name = getValueOr(wthData, "wst_name", "");
          if (wst_name.matches("(\\w{4})|(\\w{8})")) {
              return wst_name;
          }
  
          String wst_id = getValueOr(wthData, "wst_id", "");
          if (wst_id.matches("(\\w{4})|(\\w{8})")) {
              return wst_id;
          }
  
          wst_id = getValueOr(wthData, "dssat_insi", "");
          if (wst_id.matches("(\\w{4})|(\\w{8})")) {
              return wst_id;
          }
  
          return "";
      }
docs: Get the 4-bit institute code for weather file nam
  
  @param wthData weather data holder
  @return the 4-bit institute code