rules:
  - id: use-onetoonefield
    patterns:
      - pattern-inside: |
          class $M(...):
            ...
      - pattern: $F = django.db.models.ForeignKey(..., unique=True, ...)
    message: >-
      Use 'django.db.models.OneToOneField' instead of 'ForeignKey' with unique=True.
      'OneToOneField' is used to create one-to-one relationships.
    languages: [python]
    severity: WARNING
    metadata:
      category: best-practice
      technology:
        - django