code: @SuppressWarnings("unchecked")
    public Request addParameter(String name, Object value) {
      Map<String, Object> map = Objects.requireNonNull(parameterMap);
      if (!map.containsKey(name)) {
        map.put(name, value);
      } else {
        Object value0 = map.get(name);
        if (value0 instanceof Collection) {
          if (value instanceof Collection) {
            ((Collection) value0).addAll((Collection) value);
          } else {
            ((Collection) value0).add(value);
          }
        } else {
          List<Object> paramArray = new LinkedList<>();
          if (value instanceof Collection) {
            paramArray.addAll((Collection) value);
          } else {
            paramArray.add(value);
          }
          map.put(name, paramArray);
        }
      }
      return this;
    }
docs: 添加请求参数
  
  @param name 请求参数名称
  @param value 参数值