Update unit2/llama-index/workflows.ipynb

Add missing loop input for the step 1 in loop and branches code block.

unit2/llama-index/workflows.ipynb

@@ -182,7 +182,7 @@
     "\n",
     "class MultiStepWorkflow(Workflow):\n",
     "    @step\n",
-    "    async def step_one(self, ev: StartEvent) -> ProcessingEvent | LoopEvent:\n",
+    "    async def step_one(self, ev: StartEvent | LoopEvent) -> ProcessingEvent | LoopEvent:\n",
     "        if random.randint(0, 1) == 0:\n",
     "            print(\"Bad thing happened\")\n",
     "            return LoopEvent(loop_output=\"Back to step one.\")\n",