def list_overlay_names(self):
        """Return list of overlay names."""

        bucket = self.s3resource.Bucket(self.bucket)

        overlay_names = []
        for obj in bucket.objects.filter(
            Prefix=self.overlays_key_prefix
        ).all():

            overlay_file = obj.key.rsplit('/', 1)[-1]
            overlay_name, ext = overlay_file.split('.')
            overlay_names.append(overlay_name)

        return overlay_names