UnityGame/Library/PackageCache/com.unity.shadergraph/Editor/Data/Graphs/PreviewMode.cs

namespace UnityEditor.ShaderGraph
{
    enum PreviewMode
    {
        Inherit,   // this usually means: 2D, unless a connected input node is 3D, in which case it is 3D
        Preview2D,
        Preview3D
    }
}