def preload_keys(amount = 12)
      keys = EncryptedStore::ActiveRecord.preload_keys(amount)
      keys.each { |k| (@_decrypted_keys ||= {})[k.id] = k.decrypted_key }
    end
def preload_keys(amount = 12)
      keys = EncryptedStore::ActiveRecord.preload_keys(amount)
      keys.each { |k| (@_decrypted_keys ||= {})[k.id] = k.decrypted_key }
    end
Preloads the most recent `amount` keys.