Can't add academy script to academy

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Unity.MLAgents;
public class PigAcademy : Academy
{
}
this is my academy code, just a empty class,
and the error is ---- 'Academy' does not contain a constructor that takes 0 arguments

 

There is no need to inherit Academy
use Academy.Instance

 

And how to use Academy.Instance ? As there is no documentation present on academy

 

//Initialize
m_ResetParams = Academy.Instance.EnvironmentParameters;

//SetResetParameters
m_BlockRb.drag = m_ResetParams.GetWithDefault("block_drag", 0.5f);

for randomize trainer, other usage unknown