[Feat] Return hidden states (experimental) (#3364)

Co-authored-by: Chayenne <zhaochen20@outlook.com>

docs/backend/offline_engine_api.ipynb

@@ -179,6 +179,59 @@
     "asyncio.run(main())"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "llm.shutdown()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Return Hidden States"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import sglang as sgl\n",
+    "\n",
+    "llm = sgl.Engine(\n",
+    "    model_path=\"meta-llama/Meta-Llama-3.1-8B-Instruct\", return_hidden_states=True\n",
+    ")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "prompts = [\n",
+    "    \"Hello, my name is\",\n",
+    "    \"The president of the United States is\",\n",
+    "    \"The capital of France is\",\n",
+    "    \"The future of AI is\",\n",
+    "]\n",
+    "\n",
+    "sampling_params = {\"temperature\": 0.8, \"top_p\": 0.95, \"max_new_tokens\": 10}\n",
+    "\n",
+    "outputs = llm.generate(prompts, sampling_params=sampling_params)\n",
+    "for prompt, output in zip(prompts, outputs):\n",
+    "    print(\"===============================\")\n",
+    "    print(\n",
+    "        f\"Prompt: {prompt}\\nGenerated text: {output['text']}\\nPrompt_Tokens: {output['meta_info']['prompt_tokens']}\\tCompletion_tokens: {output['meta_info']['completion_tokens']}\\nHidden states: {[i.shape for i in output['meta_info']['hidden_states']]}\"\n",
+    "    )\n",
+    "    print()"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,