Based on the issue description, I need to create a patch for Django's `ManyToManyRel` class. The issue states that `through_fields` can be a list, and when hashing the identity property, it fails because lists are unhashable. The solution is to add `make_hashable` call on `self.through_fields`.

Let me understand the Django codebase structure by looking at the issue. The error trace mentions:
- `/django/db/models/fields/reverse_related.py` - where `ManyToManyRel` and `__hash__` are defined

From the issue, I know:
1. The `identity` property is used for hashing `ForeignObjectRel` objects
2. `make_hashable` is already called for `limit_choices_to` 
3. `through_fields` can be a list and needs `make_hashable` too

The fix should be in the `identity` property of `ManyToManyRel` class. Based on standard Django codebase structure and the issue description, here's the patch:

--- a/django/db/models/fields/reverse_related.py
+++ b/django/db/models/fields/reverse_related.py
@@ -310,6 +310,6 @@ class ManyToManyRel(ForeignObjectRel):
             self.through,
             self.through_fields,
             self.db_constraint,
-        )
+        ) + (make_hashable(self.through_fields),)
 
     def get_related_field(self):

Wait, that doesn't look right. Let me reconsider. Looking at the issue more carefully, the identity property returns a tuple that includes `self.through_fields` which can be a list. The fix is to wrap `self.through_fields` with `make_hashable()`.

Based on typical Django structure, the `identity` property in `ManyToManyRel` would look something like:

```python
@cached_property
def identity(self):
    return super().identity + (
        self.through,
        self.through_fields,
        self.db_constraint,
    )
```

And it should be:

```python
@cached_property
def identity(self):
    return super().identity + (
        self.through,
        make_hashable(self.through_fields),
        self.db_constraint,
    )
```

--- a/django/db/models/fields/reverse_related.py
+++ b/django/db/models/fields/reverse_related.py
@@ -310,7 +310,7 @@ class ManyToManyRel(ForeignObjectRel):
     def identity(self):
         return super().identity + (
             self.through,
-            self.through_fields,
+            make_hashable(self.through_fields),
             self.db_constraint,
         )