code: public <T> T get(String key, Class<T> clazz, T defaultValue) {
          Object obj = argMap.get(key);
          if (obj == null) {
              return defaultValue;
          }
          return Reflection.toType(obj, clazz);
      }
docs: Get the specified key's value from the unit input, anc cast it into the type you want.
  
  @return read value from the argMap, if the key doesn't exist or the key's value is null，then the defaultValue is returned.