Function is_tree_node 

pub fn is_tree_node(data: &[u8]) -> bool

Check if data is a MessagePack-encoded tree node (vs raw blob) Tree-shaped data with unsupported types still counts as a tree node so callers that subsequently decode it surface a codec error instead of reinterpreting the bytes as a raw blob. Note: Prefer try_decode_tree_node() to avoid double decoding