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

 import os
 import weakref
 
+import nest_asyncio
+
+nest_asyncio.apply()
+
 from sglang.utils import execute_shell_command, reserve_port
 
 DEFAULT_MAX_RUNNING_REQUESTS = 200

python/sglang/srt/openai_api/adapter.py

@@ -26,13 +26,6 @@ from fastapi import HTTPException, Request, UploadFile
 from fastapi.responses import ORJSONResponse, StreamingResponse
 from pydantic import ValidationError
 
-try:
-    from outlines.fsm.json_schema import convert_json_schema_to_str
-except ImportError:
-    # Before outlines 0.0.47, convert_json_schema_to_str is under
-    # outlines.integrations.utils
-    from outlines.integrations.utils import convert_json_schema_to_str
-
 from sglang.srt.code_completion_parser import (
     generate_completion_prompt_from_request,
     is_completion_template_defined,
@@ -79,7 +72,7 @@ from sglang.srt.openai_api.protocol import (
     UsageInfo,
 )
 from sglang.srt.reasoning_parser import ReasoningParser
-from sglang.utils import get_exception_traceback
+from sglang.utils import convert_json_schema_to_str, get_exception_traceback
 
 logger = logging.getLogger(__name__)
 

python/sglang/utils.py

@@ -22,6 +22,7 @@ from typing import Any, Callable, List, Optional, Tuple, Type, Union
 import numpy as np
 import requests
 from IPython.display import HTML, display
+from pydantic import BaseModel
 from tqdm import tqdm
 
 from sglang.srt.utils import kill_process_tree
@@ -29,6 +30,36 @@ from sglang.srt.utils import kill_process_tree
 logger = logging.getLogger(__name__)
 
 
+def convert_json_schema_to_str(json_schema: Union[dict, str, Type[BaseModel]]) -> str:
+    """Convert a JSON schema to a string.
+    Parameters
+    ----------
+    json_schema
+        The JSON schema.
+    Returns
+    -------
+    str
+        The JSON schema converted to a string.
+    Raises
+    ------
+    ValueError
+        If the schema is not a dictionary, a string or a Pydantic class.
+    """
+    if isinstance(json_schema, dict):
+        schema_str = json.dumps(json_schema)
+    elif isinstance(json_schema, str):
+        schema_str = json_schema
+    elif issubclass(json_schema, BaseModel):
+        schema_str = json.dumps(json_schema.model_json_schema())
+    else:
+        raise ValueError(
+            f"Cannot parse schema {json_schema}. The schema must be either "
+            + "a Pydantic class, a dictionary or a string that contains the JSON "
+            + "schema specification"
+        )
+    return schema_str
+
+
 def get_exception_traceback():
     etype, value, tb = sys.exc_info()
     err_str = "".join(traceback.format_exception(etype, value, tb))