com.unity.ml-agents/Editor/AgentEditor.cs

using UnityEngine;
using UnityEditor;

namespace Unity.MLAgents.Editor
{
    /*
     This code is meant to modify the behavior of the inspector on Agent Components.
    */
    [CustomEditor(typeof(Agent), true)]
    [CanEditMultipleObjects]
    internal class AgentEditor : UnityEditor.Editor
    {
        public override void OnInspectorGUI()
        {
            var serializedAgent = serializedObject;
            serializedAgent.Update();

            var maxSteps = serializedAgent.FindProperty("MaxStep");

            EditorGUILayout.PropertyField(
                maxSteps,
                new GUIContent("Max Step", "The per-agent maximum number of steps.")
            );

            serializedAgent.ApplyModifiedProperties();

            EditorGUILayout.LabelField("", GUI.skin.horizontalSlider);
            base.OnInspectorGUI();
        }
    }
}