docs: add example on using Langfuse as OpenTelemetry backend

python/packages/autogen-core/docs/src/user-guide/core-user-guide/framework/telemetry.md

@@ -67,3 +67,100 @@ single_threaded_runtime = SingleThreadedAgentRuntime(tracer_provider=tracer_prov
 # or for worker runtime
 worker_runtime = GrpcWorkerAgentRuntime(tracer_provider=tracer_provider)
 ```
+
+## Example using Langfuse as OpenTelemetry Backend
+
+Set your [Langfuse](https://github.com/langfuse/langfuse) API keys and configure OpenTelemetry export settings to send traces to the Langfuse OpenTelemetry backend. Please refer to the [Langfuse OpenTelemetry Docs](https://langfuse.com/docs/opentelemetry/get-started) for more information on this endpoint `/api/public/otel` authentication.
+
+```python
+import os
+import base64
+
+# Get keys for your project from the project settings page https://cloud.langfuse.com
+os.environ["LANGFUSE_PUBLIC_KEY"] = "pk-lf-..." 
+os.environ["LANGFUSE_SECRET_KEY"] = "sk-lf-..." 
+os.environ["LANGFUSE_HOST"] = "https://cloud.langfuse.com" # 🇪🇺 EU region
+# os.environ["LANGFUSE_HOST"] = "https://us.cloud.langfuse.com" # 🇺🇸 US region
+
+LANGFUSE_AUTH = base64.b64encode(
+    f"{os.environ.get('LANGFUSE_PUBLIC_KEY')}:{os.environ.get('LANGFUSE_SECRET_KEY')}".encode()
+).decode()
+
+os.environ["OTEL_EXPORTER_OTLP_ENDPOINT"] = os.environ.get("LANGFUSE_HOST") + "/api/public/otel"
+os.environ["OTEL_EXPORTER_OTLP_HEADERS"] = f"Authorization=Basic {LANGFUSE_AUTH}"
+
+# your openai key
+os.environ["OPENAI_API_KEY"] = "sk-proj-..."
+```
+
+Configure `tracer_provider` and add a span processor to export traces to Langfuse. `OTLPSpanExporter()` uses the endpoint and headers from the environment variables.
+
+```python
+from opentelemetry.sdk.trace import TracerProvider
+from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter
+from opentelemetry.sdk.trace.export import SimpleSpanProcessor
+
+trace_provider = TracerProvider()
+trace_provider.add_span_processor(SimpleSpanProcessor(OTLPSpanExporter()))
+
+# Sets the global default tracer provider
+from opentelemetry import trace
+trace.set_tracer_provider(trace_provider)
+
+# Creates a tracer from the global tracer provider
+tracer = trace.get_tracer(__name__)
+```
+
+Initialize OpenLit to start capturing OpenTelemetry traces.
+
+```python
+import openlit
+
+# Initialize OpenLIT instrumentation. The disable_batch flag is set to true to process traces immediately.
+openlit.init(tracer=tracer, disable_batch=True)
+```
+
+We'll create a simple AutoGen application where an Assistant agent answers a user's question.
+
+
+```python
+import autogen
+from autogen import AssistantAgent, UserProxyAgent
+
+llm_config = {"model": "gpt-4o", "api_key": os.environ["OPENAI_API_KEY"]}
+assistant = AssistantAgent("assistant", llm_config=llm_config)
+
+user_proxy = UserProxyAgent(
+    "user_proxy", code_execution_config={"executor": autogen.coding.LocalCommandLineCodeExecutor(work_dir="coding")}
+)
+
+# Start the chat
+user_proxy.initiate_chat(
+    assistant,
+    message="What is Langfuse?",
+)
+```
+
+Opentelemetry lets you attach a set of attributes to all spans by setting [`set_attribute`](https://opentelemetry.io/docs/languages/python/instrumentation/#add-attributes-to-a-span). This allows you to set properties like a Langfuse Session ID, to group traces into Langfuse Sessions or a User ID, to assign traces to a specific user. You can find a list of all supported attributes in the [here](/docs/opentelemetry/get-started#property-mapping).
+
+
+```python
+with tracer.start_as_current_span("AutoGen-Trace") as span:
+    span.set_attribute("langfuse.user.id", "user-123")
+    span.set_attribute("langfuse.session.id", "123456789")
+    span.set_attribute("langfuse.tags", ["semantic-kernel", "demo"])
+    span.set_attribute("langfuse.prompt.name", "test-1")
+
+    # Start the chat
+    user_proxy.initiate_chat(
+        assistant,
+        message="What is Langfuse?",
+    )
+```
+
+After running the agent above, you can log in to your Langfuse dashboard and view the traces generated by your AutoGen application. Here is an example screenshot of a trace in Langfuse:
+
+![Langfuse Trace](https://langfuse.com/images/cookbook/integration-autogen/autogen-example-trace.png)
+
+You can also view the public trace here: [Langfuse Trace Example](https://cloud.langfuse.com/project/cloramnkj0002jz088vzn1ja4/traces/df850ab499107d4348584cf5933baabd?timestamp=2025-02-04T16%3A55%3A51.660Z&observation=286c648acb0105c2)
+