src/vs/workbench/api/common/extHostComments.ts/ExtHostCommentThread/collapsibleState
class ExtHostCommentThread:	set collapsibleState(newState: vscode.CommentThreadCollapsibleState) {
		this._collapseState = newState;
		this.modifications.collapsibleState = newState;
		this._onDidUpdateCommentThread.fire();
	}