Missing models import in generated migration file

[archie-ai-code-explain-pr-review]

• The issue is that the generated migration file is missing an import statement for the models module, which is causing a NameError when trying to use models.Model in the migration.
• The provided code in models.py defines a custom MyField that inherits from models.TextField, a MyBaseModel that inherits from models.Model, and a MyModel that inherits from both MyMixin and MyBaseModel.
• When running the makemigrations command, Django generates a migration file 0001_initial.py that includes the MyModel definition, but it fails to include the necessary import statement for the models module.
• The expected behavior is for Django to generate a valid Python migration file that includes the necessary import statements. The actual behavior is that the generated migration file is missing the import statement, causing the NameError when trying to use models.Model.