ml-agents/UnitySDK/Assets/ML-Agents/Examples/Reacher/Scripts/ReacherAcademy.cs

using UnityEngine;
using MLAgents;

public class ReacherAcademy : Academy
{
    public override void AcademyReset()
    {
        Physics.gravity = new Vector3(0, -resetParameters["gravity"], 0);
    }

    public override void AcademyStep()
    {
    }
}