What is the OpenAI Realtime API and what use cases does it enable?

import asyncio
import websockets
import json

# Realtime API uses WebSocket connection:
async def realtime_session():
    url = "wss://api.openai.com/v1/realtime?model=gpt-realtime-2"
    headers = {
        "Authorization": f"Bearer {OPENAI_API_KEY}",
        "OpenAI-Beta": "realtime=v1"
    }
    async with websockets.connect(url, extra_headers=headers) as ws:
        # Configure session
        await ws.send(json.dumps({
            "type": "session.update",
            "session": {
                "modalities": ["text", "audio"],
                "voice": "alloy",
                "instructions": "You are a helpful coding assistant.",
                "input_audio_format": "pcm16",
                "output_audio_format": "pcm16",
            }
        }))
        # Stream audio input
        await ws.send(json.dumps({
            "type": "input_audio_buffer.append",
            "audio": base64_pcm16_audio_chunk,
        }))
        # Commit and request response
        await ws.send(json.dumps({"type": "input_audio_buffer.commit"}))
        await ws.send(json.dumps({"type": "response.create"}))