ImageGenerationStreamEvent

{
    "type": "image_generation.completed",
    "created_at": 0,
    "usage": {
        "prompt_tokens": 0,
        "completion_tokens": 0,
        "output_tokens": 0,
        "total_tokens": 0,
        "prompt_tokens_details": {
            "property1": "string",
            "property2": "string"
        },
        "completion_tokens_details": {
            "property1": "string",
            "property2": "string"
        },
        "property1": "string",
        "property2": "string"
    },
    "url": "http://example.com",
    "property1": "string",
    "property2": "string"
}