default_attachments not passing query string parameters to get_lookup_choices

[davidoj]

The TypedAttachmentListSerializer class currently defines default attachments to call get_lookup_choices with an empty context:

def default_attachments(self, initial):
    """ """
    types = self.child.get_lookup_choices(type_field, {})

The empty context is passed through to compute_filter unchanged, so it does not filter on query string parameters (or anything else) as I believe it is intended to.