def initial(self, request, *args, **kwargs):
        """
        Overrides DRF's `initial` in order to set the `_sorting_field` from corresponding property in view.
        Protected property is required in order to support overriding of `sorting_field` via `@property`, we do this
        after original `initial` has been ran in order to make sure that view has all its properties set up.
        """
        super(FlatMultipleModelMixin, self).initial(request, *args, **kwargs)
        assert not (self.sorting_field and self.sorting_fields), \
            '{} should either define ``sorting_field`` or ``sorting_fields`` property, not both.' \
            .format(self.__class__.__name__)
        if self.sorting_field:
            warnings.warn(
                '``sorting_field`` property is pending its deprecation. Use ``sorting_fields`` instead.',
                DeprecationWarning
            )
            self.sorting_fields = [self.sorting_field]
        self._sorting_fields = self.sorting_fields
Overrides DRF's `initial` in order to set the `_sorting_field` from corresponding property in view.
        Protected property is required in order to support overriding of `sorting_field` via `@property`, we do this
        after original `initial` has been ran in order to make sure that view has all its properties set up.