code: public static KV<String, Forest> remove(String key) {
          KV<String, Forest> kv = AMBIGUITY.get(key);
          if (kv != null && kv.getV() != null) {
              kv.getV().clear();
          }
          MyStaticValue.ENV.remove(key);
          return AMBIGUITY.remove(key);
      }
docs: 删除一个key
  
  @param key
  @return