ScriptableRenderPipeline/MaterialGraphProject/Assets/UnityShaderEditor/Runtime/Graphs/AbstractMaterialGraph.cs

using System;
using UnityEngine.Graphing;

namespace UnityEngine.MaterialGraph
{
    [Serializable]
    public abstract class AbstractMaterialGraph : SerializableGraph
    {
        public override void AddNode(INode node)
        {
            if (node is AbstractMaterialNode)
            {
                base.AddNode(node);
            }
            else
            {
                Debug.LogWarningFormat("Trying to add node {0} to Material graph, but it is not a {1}", node, typeof(AbstractMaterialNode));
            }
        }
    }
}