Function initial_root 

pub fn initial_root<F, K, V, H>() -> H::Digest
where
    F: Family,
    K: Key,
    V: ValueEncoding,
    H: Hasher,
    Operation<F, K, V>: EncodeShared,

Compute the authenticated root of a newly initialized database without opening storage.

The initial commit never carries metadata, so this root always represents Commit(None, 0).