Steps to reproduce:
1) Create a new project
2) Window > Package Manager > Install Visual Effect Graph
3) Import VisualEffectGraph addition sample

Actual result: ArgumentException and Serialization errors are thrown on importing the package

Expected result: No errors should be thrown in console

Occurring on: 2020.2.0a7 with VFX version 9.0.0-preview.14, 2020.1.0b5 with VFX version 8.0.1, 2020.1.0a24 with VFX version 7.1.8

Working fine on: 2019.3.10f1 with URP version 7.3.1

Environment: Both Windows and Mac

Stack Trace:
1) ArgumentException: Can not deserialize (UnityEditor.Rendering.HighDefinition.HDPBRSubShader), type is invalid
UnityEditor.Graphing.SerializationHelper.Deserialize[T] (UnityEditor.Graphing.SerializationHelper+JSONSerializedElement item, System.Collections.Generic.Dictionary`2[TKey,TValue] remapper, System.Object[] constructorArgs) (at Library/PackageCache/com.unity.shadergraph@7.1.8/Editor/Data/Util/SerializationHelper.cs:124)
UnityEditor.Graphing.SerializationHelper.Deserialize[T] (System.Collections.Generic.IEnumerable`1[T] list, System.Collections.Generic.Dictionary`2[TKey,TValue] remapper, System.Object[] constructorArgs) (at Library/PackageCache/com.unity.shadergraph@7.1.8/Editor/Data/Util/SerializationHelper.cs:157)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&)

2)
{}
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&)