def METHOD_NAME(self, value):
    if isinstance(value, list) and len(value) == 2 and isinstance(value[0], str):
        filename, payload = value
        try:
            payload = base64.b64decode(payload)
        except TypeError:
            pass
        else:
            if self.storage.exists(filename):
                self.storage.delete(filename)
            self.storage.save(filename, ContentFile(payload))
            return filename
    return value