fix: fix ipython running error for Engine due to outlines nest_asyncio (#4582)

Co-authored-by: shuaills <shishuaiuoe@gmail.com>

docs/backend/offline_engine_api.ipynb

@@ -19,12 +19,7 @@
     "- Streaming asynchronous generation\n",
     "\n",
     "Additionally, you can easily build a custom server on top of the SGLang offline engine. A detailed example working in a python script can be found in [custom_server](https://github.com/sgl-project/sglang/blob/main/examples/runtime/engine/custom_server.py).\n",
-    "\n",
-    "## SPECIAL WARNING!!!!\n",
-    "\n",
-    "**To launch the offline engine in your python scripts,** `__main__` **condition is necessary, since we use** `spawn` **mode to create subprocesses. Please refer to this simple example**:\n",
-    "\n",
-    "https://github.com/sgl-project/sglang/blob/main/examples/runtime/engine/launch_engine.py"
+    "\n"
    ]
   },
   {

docs/backend/patch.py

@@ -1,6 +1,10 @@
 import os
 import weakref
 
+import nest_asyncio
+
+nest_asyncio.apply()
+
 from sglang.utils import execute_shell_command, reserve_port
 
 DEFAULT_MAX_RUNNING_REQUESTS = 200