class MultipartFormencodeParser(parsers.MultiPartParser):

    def parse(self, stream, media_type=None, parser_context=None):
        result = super().parse(stream, media_type=media_type,
            parser_context=parser_context)
data = variable_decode(result.data)
return parsers.DataAndFiles(data, result.files)
django rest framework file upload with nested writable serializers