Read what one group of the canvas holds: a shot's storyboard group (its panel) or production group, a story element's moodboard, storyboard or production group, or the art direction. Returns the group's nodes (generators with their prompt, the @# references it cites and their model; text nodes; the shot node with its action; image nodes; in a story element group, the Story element node first with this stage's body and its references), each image's current output as a mediaId when it has one (look at it with view_media), and the edges into and inside the group. isShotPanel marks the shot's panel generator, isStarred the generator starred as the group's output. defaultNodeId is what add_reference_images and set_prompt write to when no nodeId is given. Read-only, no credits.