Null ref exception when trying to insert edge to the graph about arangoclient.net HOT 3 CLOSED

    public class Person
    {
        [DocumentProperty(Identifier= IdentifierType.Key)]
        public string Key { get; set; }

        public string Fullname { get; set; }
    }

    public class Friend
    {
        [DocumentProperty(Identifier = IdentifierType.EdgeFrom)]
        public string From { get; set; }

        [DocumentProperty(Identifier = IdentifierType.EdgeTo)]
        public string To { get; set; }

        public string Message { get; set; }
    }

                var p1 = new Person { Fullname = "raoof" };
                var p2 = new Person { Fullname = "drgraduss" };

                db.Insert<Person>(p1);
                db.Insert<Person>(p2);

                var friend = new Friend { Message = "lets be friends" };

                db.InsertEdge<Friend, Person, Person>(p1.Key, p2.Key, friend);

                Debug.Assert(p1.Key != null);
                Debug.Assert(p2.Key != null);
                Debug.Assert(friend.From != null);
                Debug.Assert(friend.To != null);

// change settings for collections
sharedSetting.Collection.ChangeCollectionPropertyForType<Product>(p =>
                {
                    p.CollectionName = "products";
                    p.Naming = NamingConvention.ToCamelCase;
                });

// change default Idetntifier for `_key` property for all types
sharedSetting.Collection.ChangeIdentifierDefaultName(IdentifierType.Key, "Key");

// change default Idetntifier for `_key` property for specific type
sharedSetting.Collection.ChangeDocumentPropertyForType<Product>(p => p.productKey, s => {
                    {
                        s.Identifier = IdentifierType.Key;
                    }});