ledger

type Ledger interface {
	// Put adds or overwrites a key in the Ledger
	Put(key, value string) (string, error)
	// Delete removes a key from the Ledger, which may still be read using GetPreviousValue
	Delete(key string) error
	// Get returns a the value of the key from the Ledger's current state
	Get(key string) (string, error)
	// RootHash is the hash of all keys and values currently in the Ledger
	RootHash() string
	// GetPreviousValue executes a get against a previous version of the ledger, using that version's root hash.
	GetPreviousValue(previousRootHash, key string) (result string, err error)
}