This is probably not a high traffic pipeline, but I have noticed it is probably possible for this pipeline to inherit FromSingleFileMixin harmlessly, it currently does not.
I am using this snippet to support single file loads with this pipeline and it seems to work fine when it inherits this mixin.
pipe_class = type(
'StableDiffusionAdapterPipeline',
(diffusers.loaders.FromSingleFileMixin, diffusers.StableDiffusionAdapterPipeline), {})
pipe_class.from_single_file(...)