Accumulator is a proof of a single element's existance in a Merkle tree accumulator.

AccumulatorRange is a proof that a consecutive list of elements exist in a Merkle tree accumulator.

LeafNode of a sparse Merkle tree.

SparseMerkle is a proof that an element exists in a sparse Merkle tree, or an element key does not exist in the tree.

HashValue is equivalent to sha3libra.HashValue, which is []byte.