Node.layers' default: the default layer and nothing else.
A node belongs to exactly one layer until an author says otherwise, which is
what makes the whole mechanism opt-in — every mask that has ever been handed
out contains this bit unless it was built to exclude it.
Node.layers' default: the default layer and nothing else.A node belongs to exactly one layer until an author says otherwise, which is what makes the whole mechanism opt-in — every mask that has ever been handed out contains this bit unless it was built to exclude it.