Based on the issue description and my knowledge of the Django codebase, I can generate the fix. The issue is that the `AutoFieldMeta` metaclass has a `_subclasses` property that only includes `AutoField`, `BigAutoField`, and `SmallAutoField` directly, but doesn't properly handle subclasses of `BigAutoField` and `SmallAutoField` in its `__subclasscheck__` method.

The problem is in `django/db/models/fields/__init__.py`. The `_subclasses` property returns a tuple with just the three base auto field classes, and the `__subclasscheck__` method only checks if a class is a subclass of `AutoField` but doesn't account for the fact that `BigAutoField` and `SmallAutoField` have their own subclasses that should also be considered valid.

Looking at the error message and the traceback, the fix needs to be in the `AutoFieldMeta.__subclasscheck__` method. The current implementation likely only checks against `AutoField` directly, but since `BigAutoField` and `SmallAutoField` are siblings of `AutoField` (both inherit from `AutoFieldMixin` and `IntegerField`/`BigIntegerField`/`SmallIntegerField`), their subclasses aren't properly recognized.

The fix is to modify the `_subclasses` property in `AutoFieldMeta` to include `BigAutoField` and `SmallAutoField` so that the `__subclasscheck__` method properly recognizes subclasses of these fields as valid auto fields.

--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -2551,6 +2551,8 @@ class AutoFieldMeta(type):
     @property
     def _subclasses(self):
         return (AutoField, BigAutoField, SmallAutoField)
+        return (AutoField, BigAutoField, SmallAutoField) + tuple(
+            cls for cls in (BigAutoField, SmallAutoField) for cls in cls.__subclasses__()
+        )
 
     def __instancecheck__(self, instance):
         return isinstance(instance, self._subclasses) or super().__instancecheck__(instance)

Wait, that's not correct. Let me reconsider the issue more carefully.

Looking at the problem: When you have `class MyBigAutoField(models.BigAutoField)`, the `__subclasscheck__` method needs to return `True` when checking if `MyBigAutoField` is a subclass of `AutoField`. 

The current implementation of `__subclasscheck__` likely does something like:
```python
def __subclasscheck__(self, subclass):
    return subclass in self._subclasses or super().__subclasscheck__(subclass)
```

But the issue is that `BigAutoField` and `SmallAutoField` don't actually inherit from `AutoField` - they all inherit from `AutoFieldMixin`. So when checking `issubclass(MyBigAutoField, AutoField)`, Python's normal `issubclass` won't work because `BigAutoField` is not a subclass of `AutoField`.

The fix should modify the `__subclasscheck__` to check if the class is a subclass of any class in `_subclasses`, not just if it's in `_subclasses`:

--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -2555,4 +2555,4 @@ class AutoFieldMeta(type):
         return isinstance(instance, self._subclasses) or super().__instancecheck__(instance)
 
     def __subclasscheck__(self, subclass):
-        return subclass in self._subclasses or super().__subclasscheck__(subclass)
+        return issubclass(subclass, self._subclasses) or super().__subclasscheck__(subclass)

Hmm, but this might cause infinite recursion. Let me think about this more carefully.

The metaclass `AutoFieldMeta` is used by `AutoField`. The `_subclasses` property returns `(AutoField, BigAutoField, SmallAutoField)`. 

When checking `issubclass(MyBigAutoField, AutoField)`:
1. Python calls `AutoFieldMeta.__subclasscheck__(AutoField, MyBigAutoField)`
2. Current implementation: `MyBigAutoField in (AutoField, BigAutoField, SmallAutoField)` - this is `False`
3. Then it calls `super().__subclasscheck__(MyBigAutoField)` which is `type.__subclasscheck__` - this checks if `MyBigAutoField` is in `AutoField.__mro__`, which it isn't.

The fix should check if `MyBigAutoField` is a subclass of any of the classes in `_subclasses`. We need to use the standard `type.__subclasscheck__` to avoid recursion:

```python
def __subclasscheck__(self, subclass):
    return any(
        type.__subclasscheck__(cls, subclass) for cls in self._subclasses
    ) or super().__subclasscheck__(subclass)
```

Or more simply, since `issubclass` on regular classes (not the metaclass) should work:

```python
def __subclasscheck__(self, subclass):
    return issubclass(subclass, self._subclasses) or super().__subclasscheck__(subclass)
```

Wait, but this could cause recursion if `subclass` also uses `AutoFieldMeta`. Let me think again...

Actually, `issubclass(MyBigAutoField, BigAutoField)` would work correctly because `BigAutoField` uses the regular `type` metaclass for this check, and `MyBigAutoField` inherits from `BigAutoField`. 

The issue is that `BigAutoField` and `SmallAutoField` classes themselves don't use `AutoFieldMeta` as their metaclass - only `AutoField` does. So `issubclass(subclass, self._subclasses)` should work correctly without causing infinite recursion.

Let me verify this understanding and create the correct patch:

--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -2555,4 +2555,4 @@ class AutoFieldMeta(type):
         return isinstance(instance, self._subclasses) or super().__instancecheck__(instance)
 
     def __subclasscheck__(self, subclass):
-        return subclass in self._subclasses or super().__subclasscheck__(subclass)
+        return issubclass(subclass, self._subclasses) or super().__subclasscheck__(subclass)

But wait, I need to double-check. Looking at Django's structure:
- `AutoField` has `AutoFieldMeta` as its metaclass
- `BigAutoField` and `SmallAutoField` also need to be checked

If `BigAutoField` also uses `AutoFieldMeta`, then `issubclass(MyBigAutoField, BigAutoField)` would call `AutoFieldMeta.__subclasscheck__` again, potentially causing issues.

Actually, looking more carefully at Django's code structure, `BigAutoField` and `SmallAutoField` would inherit the metaclass from their parent class. But since they inherit from `BigIntegerField` and `SmallIntegerField` respectively (which don't use `AutoFieldMeta`), and `AutoFieldMixin`, the metaclass situation is more complex.

Let me use a safer approach that avoids the potential recursion by using `super().__subclasscheck__` which delegates to `type.__subclasscheck__`:

```python
def __subclasscheck__(self, subclass):
    return any(
        super().__subclasscheck__(subclass) if cls is self else issubclass(subclass, cls)
        for cls in self._subclasses
    ) or super().__subclasscheck__(subclass)
```

Actually, the simplest fix that matches the description in the issue is to just use `issubclass` directly:

--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -2555,4 +2555,4 @@ class AutoFieldMeta(type):
         return isinstance(instance, self._subclasses) or super().__instancecheck__(instance)
 
     def __subclasscheck__(self, subclass):
-        return subclass in self._subclasses or super().__subclasscheck__(subclass)
+        return issubclass(subclass, self._subclasses) or super().__subclasscheck__(subclass)

This should work because:
1. `issubclass(MyBigAutoField, (AutoField, BigAutoField, SmallAutoField))` will return `True` because `MyBigAutoField` is a subclass of `BigAutoField`
2. Since `BigAutoField` doesn't use `AutoFieldMeta` as its metaclass (it inherits from `BigIntegerField`), there's no recursion issue

--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -2551,7 +2551,7 @@ class AutoFieldMeta(type):
     @property
     def _subclasses(self):
         return (AutoField, BigAutoField, SmallAutoField)

     def __instancecheck__(self, instance):
         return isinstance(instance, self._subclasses) or super().__instancecheck__(instance)

     def __subclasscheck__(self, subclass):
-        return subclass in self._subclasses or super().__subclasscheck__(subclass)
+        return issubclass(subclass, self._subclasses) or super().__subclasscheck__(subclass)