apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/environment/Env.java/Env/transformEnv
class Env:  public static Env transformEnv(String envName) {
    final String envWellFormName = getWellFormName(envName);
    // special case for production in case of typo
    if ("PROD".equalsIgnoreCase(envWellFormName)) {
      return Env.PRO;
    }

    // special case that FAT & FWS should map to FAT
    if ("FWS".equalsIgnoreCase(envWellFormName)) {
      return Env.FAT;
    }

    if (Env.exists(envWellFormName)) {
      return Env.valueOf(envWellFormName);
    }
    // cannot be found or blank name
    return Env.UNKNOWN;
  }