pub fn merkle_root_and_path_by_absolute_index(&self, index: usize) -> (H256, Vec<H256>) {
        assert!(index >= self.start_index, "leaf is cached");
        self.merkle_root_and_path(index - self.start_index)
    }
Returns the root hash and the Merkle proof for a leaf with the specified 0-based `index`.
`index` is an absolute position of the leaf.
# Panics
Panics if leaf at `index` is cached or if `index` is >= than the number of leaves in the tree.
core/lib/mini_merkle_tree/src/lib.rs