Add additonal ruling

Author: inputfalken

src/DynamoDBGenerator.SourceGenerator/Generations/Marshalling/Marshaller.cs

@@ -215,9 +215,7 @@ internal static string InvokeMarshallerMethod(ITypeSymbol typeSymbol, string par
             return invocation;
 
         if (typeSymbol.TypeIdentifier() is UnknownType)
-            return typeSymbol.IsNullable()
-                ? $"{AttributeValueUtilityFactory.ToAttributeValue}({invocation})"
-                : $"new {Constants.AWSSDK_DynamoDBv2.AttributeValue} {{ M = {invocation} }}";
+            return $"{AttributeValueUtilityFactory.ToAttributeValue}({invocation})";
 
         return invocation;
     }

src/DynamoDBGenerator/Internal/MarshallHelper.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Amazon.DynamoDBv2.Model;
 using static System.Runtime.InteropServices.CollectionsMarshal;
@@ -17,8 +18,11 @@ public static class MarshallHelper
 #pragma warning disable CS1591
     public static AttributeValue Null { get; } = new() { NULL = true };
 
-    public static AttributeValue? ToAttributeValue(Dictionary<string, AttributeValue>? dict) => dict is null 
-        ? null 
+    [return: NotNullIfNotNull(nameof(dict))]
+    public static AttributeValue? ToAttributeValue(
+        [NotNullIfNotNull(nameof(dict))] Dictionary<string, AttributeValue>? dict
+    ) => dict is null
+        ? null
         : new AttributeValue { M = dict };
 
     public static AttributeValue FromDictionary<T, TArgument>(