Function merkle_proof_internal 

pub fn merkle_proof_internal(
    leaves: &[Fp<MontBackend<FqConfig, 4>, 4>],
    index: usize,
) -> (Vec<Fp<MontBackend<FqConfig, 4>, 4>>, u64, usize)

Compute the Merkle path and path index bits for a given leaf index

Generates the Merkle proof for a leaf at the given index, including all sibling nodes along the path to the root and the path indices encoded as a bit pattern.

Returns

Returns a tuple containing:

• path_elements: Vector of sibling scalar values along the path
• path_indices: Path indices encoded as a u64 bit pattern
• levels: Number of levels in the tree