# Functions
CreateNextBlock provides a utility way to construct the next block from contents and metadata for a given ledger XXX This will need to be modified to accept marshaled envelopes to accommodate non-deterministic marshaling.
GetBlock is a utility method for retrieving a single block.
# Structs
NotFoundErrorIterator simply always returns an error of cb.Status_NOT_FOUND, and is generally useful for implementations of the Reader interface.
# Interfaces
Factory retrieves or creates new ledgers by chainID.
Iterator is useful for a chain Reader to stream blocks as they are created.
Reader allows the caller to inspect the ledger.
ReadWriter encapsulates the read/write functions of the ledger.
Writer allows the caller to modify the ledger.