feat: Add smart type hints to OpaqueKeyField and its subclasses

opaque_keys/edx/django/models.py

@@ -194,6 +194,9 @@ class LearningContextKeyField(OpaqueKeyField):
  """
  description = "A LearningContextKey object, saved to the DB in the form of a string"
  KEY_CLASS = LearningContextKey
+ # Declare the field types for the django-stubs mypy type hint plugin:
+ _pyi_private_set_type: LearningContextKey | str | None
+ _pyi_private_get_type: LearningContextKey
 
 
 class CourseKeyField(OpaqueKeyField):
@@ -202,6 +205,9 @@ class CourseKeyField(OpaqueKeyField):
  """
  description = "A CourseKey object, saved to the DB in the form of a string"
  KEY_CLASS = CourseKey
+ # Declare the field types for the django-stubs mypy type hint plugin:
+ _pyi_private_set_type: CourseKey | str | None
+ _pyi_private_get_type: CourseKey
 
 
 class UsageKeyField(OpaqueKeyField):
@@ -210,6 +216,9 @@ class UsageKeyField(OpaqueKeyField):
  """
  description = "A Location object, saved to the DB in the form of a string"
  KEY_CLASS = UsageKey
+ # Declare the field types for the django-stubs mypy type hint plugin:
+ _pyi_private_set_type: UsageKey | str | None
+ _pyi_private_get_type: UsageKey
 
 
 class LocationKeyField(UsageKeyField):
@@ -228,3 +237,6 @@ class BlockTypeKeyField(OpaqueKeyField):
  """
  description = "A BlockTypeKey object, saved to the DB in the form of a string."
  KEY_CLASS = BlockTypeKey
+ # Declare the field types for the django-stubs mypy type hint plugin:
+ _pyi_private_set_type: BlockTypeKey | str | None
+ _pyi_private_get_type: BlockTypeKey