versatileimagefield/registry.py
def register_sizer(self, attr_name, sizedimage_cls):
        """
        Register a new SizedImage subclass (`sizedimage_cls`).

        To be used via the attribute (`attr_name`).
        """
        if attr_name.startswith(
            '_'
        ) or attr_name in self.unallowed_sizer_names:
            raise UnallowedSizerName(
                "`%s` is an unallowed Sizer name. Sizer names cannot begin "
                "with an underscore or be named any of the "
                "following: %s." % (
                    attr_name,
                    ', '.join([
                        name
                        for name in self.unallowed_sizer_names
                    ])
                )
            )
        if not issubclass(sizedimage_cls, SizedImage):
            raise InvalidSizedImageSubclass(
                'Only subclasses of versatileimagefield.datastructures.'
                'SizedImage may be registered with register_sizer'
            )

        if attr_name in self._sizedimage_registry:
            raise AlreadyRegistered(
                'A SizedImage class is already registered to the `%s` '
                'attribute. If you would like to override this attribute, '
                'use the unregister method' % attr_name
            )
        else:
            self._sizedimage_registry[attr_name] = sizedimage_cls
def register_sizer(self, attr_name, sizedimage_cls):
        """
        Register a new SizedImage subclass (`sizedimage_cls`).

        To be used via the attribute (`attr_name`).
        """
        if attr_name.startswith(
            '_'
        ) or attr_name in self.unallowed_sizer_names:
            raise UnallowedSizerName(
                "`%s` is an unallowed Sizer name. Sizer names cannot begin "
                "with an underscore or be named any of the "
                "following: %s." % (
                    attr_name,
                    ', '.join([
                        name
                        for name in self.unallowed_sizer_names
                    ])
                )
            )
        if not issubclass(sizedimage_cls, SizedImage):
            raise InvalidSizedImageSubclass(
                'Only subclasses of versatileimagefield.datastructures.'
                'SizedImage may be registered with register_sizer'
            )

        if attr_name in self._sizedimage_registry:
            raise AlreadyRegistered(
                'A SizedImage class is already registered to the `%s` '
                'attribute. If you would like to override this attribute, '
                'use the unregister method' % attr_name
            )
        else:
            self._sizedimage_registry[attr_name] = sizedimage_cls
Register a new SizedImage subclass (`sizedimage_cls`).

        To be used via the attribute (`attr_name`).