Delete with deep = False
Sometimes we need to delete the node leaving all children in place (inserting them at the parent's place). A .delete(deep = False) will be really useful in this case.
This is low-priority enhancement because we can manually move the subtree (N children queries) and then delete the parent. With deep = False this can be done more efficient.
Alternatively .delete_node(deep = True) method can implement this functionality, such that standard .delete() will call it with deep = True. This approach avoids introducing non-standard argument to .delete() (consistency)