apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/environment/Env.java/Env/fromString
class Env:  @Deprecated
  public static Env fromString(String env) {
    Env environment = transformEnv(env);
    Preconditions.checkArgument(environment != UNKNOWN, String.format("Env %s is invalid", env));
    return environment;
  }