src/doc/doc-utils.js/breakParentGroup
function breakParentGroup(groupStack) {
  if (groupStack.length > 0) {
    const parentGroup = groupStack[groupStack.length - 1];
    // Breaks are not propagated through conditional groups because
    // the user is expected to manually handle what breaks.
    if (!parentGroup.expandedStates) {
      parentGroup.break = true;
    }
  }
  return null;
}