Return the leaf nodes in full path form
t() :: [parent: [term], node: [term], key: term, from: pid | nil]
Return the leaf nodes in full path form.
iex> SystemRegistry.Node.leaf_nodes(%{a: 2}) [[:a]]
iex> SystemRegistry.Node.leaf_nodes(%{a: %{b: 1, c: %{d: 2}}}) [[:a, :b], [:a, :c, :d]]
iex> SystemRegistry.Node.leaf_nodes(%{}) []