Update subgen.py

Re-added random import (whoops!)

subgen/subgen.py

@@ -9,6 +9,7 @@
 import logging
 import gc
 import io
+import random
 from typing import BinaryIO, Union, Any
 from fastapi import FastAPI, File, UploadFile, Query, Header, Body, Form, Request
 from fastapi.responses import StreamingResponse, RedirectResponse