[V1] Add structural_tag support using xgrammar (#17085)

examples/online_serving/openai_chat_completion_structured_outputs_structural_tag.py

@@ -0,0 +1,85 @@
+# SPDX-License-Identifier: Apache-2.0
+from openai import OpenAI
+
+# This example demonstrates the `structural_tag` response format.
+# It can be used to specify a structured output format that occurs between
+# specific tags in the response. This example shows how it could be used
+# to enforce the format of a tool call response, but it could be used for
+# any structured output within a subset of the response.
+
+
+def main():
+    client = OpenAI(
+        base_url="http://localhost:8000/v1",
+        api_key="-",
+    )
+
+    messages = [{
+        "role":
+        "user",
+        "content":
+        """
+You have access to the following function to retrieve the weather in a city:
+
+    {
+        "name": "get_weather",
+        "parameters": {
+            "city": {
+                "param_type": "string",
+                "description": "The city to get the weather for",
+                "required": True
+            }
+        }
+    }
+
+If a you choose to call a function ONLY reply in the following format:
+<{start_tag}={function_name}>{parameters}{end_tag}
+where
+
+start_tag => `<function`
+parameters => a JSON dict with the function argument name as key and function
+              argument value as value.
+end_tag => `</function>`
+
+Here is an example,
+<function=example_function_name>{"example_name": "example_value"}</function>
+
+Reminder:
+- Function calls MUST follow the specified format
+- Required parameters MUST be specified
+- Only call one function at a time
+- Put the entire function call reply on one line
+- Always add your sources when using search results to answer the user query
+
+You are a helpful assistant.
+
+Given the previous instructions, what is the weather in New York City, Boston,
+and San Francisco?
+"""
+    }]
+
+    response = client.chat.completions.create(
+        model="meta-llama/Llama-3.1-8B-Instruct",
+        messages=messages,
+        response_format={
+            "type":
+            "structural_tag",
+            "structures": [{
+                "begin": "<function=get_weather>",
+                "schema": {
+                    "type": "object",
+                    "properties": {
+                        "city": {
+                            "type": "string"
+                        }
+                    }
+                },
+                "end": "</function>"
+            }],
+            "triggers": ["<function="]
+        })
+    print(response)
+
+
+if __name__ == "__main__":
+    main()