New stream event type image_group

{
  "har.sse_event_types": [
    "conversation_detail_metadata",
    "event:delta",
    "event:delta_encoding",
    "image_group",
    "message_marker",
    "message_stream_complete",
    "resume_conversation_token",
    "server_ste_metadata",
    "stop",
    "title_generation"
  ]
}