diff --git a/src/runtime/InteropConfiguration.cs b/src/runtime/InteropConfiguration.cs
@@ -22,6 +22,7 @@ public static InteropConfiguration MakeDefault()
                {
                    DefaultBaseTypeProvider.Instance,
                    new CollectionMixinsProvider(new Lazy<PyObject>(() => Py.Import("clr._extras.collections"))),
                },
            };
        }

diff --git a/src/runtime/Mixins/dlr.py b/src/runtime/Mixins/dlr.py
@@ -0,0 +1,18 @@
diff --git a/src/runtime/PythonEngine.cs b/src/runtime/PythonEngine.cs
@@ -299,7 +299,7 @@ static void LoadSubmodule(BorrowedReference targetModuleDict, string fullName, s

        static void LoadMixins(BorrowedReference targetModuleDict)
        {
-            foreach (string nested in new[] { "collections" })
            {
                LoadSubmodule(targetModuleDict,
                    fullName: "clr._extras." + nested,

diff --git a/src/runtime/TypeManager.cs b/src/runtime/TypeManager.cs
@@ -1,9 +1,12 @@
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Diagnostics;
using Python.Runtime.Native;
using Python.Runtime.StateSerialization;

@@ -37,10 +40,190 @@ internal class TypeManager
            "tp_clear",
        };

        internal static void Initialize()
        {
            Debug.Assert(cache.Count == 0, "Cache should be empty",
                "Some errors may occurred on last shutdown");
            using (var plainType = SlotHelper.CreateObjectType())
            {
                subtype_traverse = Util.ReadIntPtr(plainType.Borrow(), TypeOffset.tp_traverse);
@@ -64,6 +247,8 @@ internal static void RemoveTypes()
                }
            }

            foreach (var type in cache.Values)
            {
                type.Dispose();
@@ -313,6 +498,13 @@ internal static void InitializeClass(PyType type, ClassBase impl, Type clrType)
                throw PythonException.ThrowLastAsClrException();
            }

            var dict = Util.ReadRef(type, TypeOffset.tp_dict);
            string mn = clrType.Namespace ?? "";
            using (var mod = Runtime.PyString_FromString(mn))

diff --git a/src/runtime/Types/ClassDerived.cs b/src/runtime/Types/ClassDerived.cs
@@ -1,6 +1,7 @@
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
@@ -232,6 +233,13 @@ internal static Type CreateDerivedType(string name,
                    continue;
                }

                // skip if this property has already been overridden
                if ((method.Name.StartsWith("get_") || method.Name.StartsWith("set_"))
                    && pyProperties.Contains(method.Name.Substring(4)))
@@ -300,6 +308,35 @@ internal static Type CreateDerivedType(string name,
            return type;
        }

        /// <summary>
        /// Add a constructor override that calls the python ctor after calling the base type constructor.
        /// </summary>
-Original file line number
+Diff line change
@@ Expand Up / @@ -22,6 +22,7 @@ public static InteropConfiguration MakeDefault() @@
                     {
                         DefaultBaseTypeProvider.Instance,
                         new CollectionMixinsProvider(new Lazy<PyObject>(() => Py.Import("clr._extras.collections"))),
                     },
                 };
             }
@@ Expand Down @@