def write(key, data = nil, parameters = {}, conditions = {})
      @stores.capture_first {|s| s.write(key, data, parameters, conditions)}
    end
def write(key, data = nil, parameters = {}, conditions = {})
      @stores.capture_first {|s| s.write(key, data, parameters, conditions)}
    end
persists the data so that it can be retrieved by the key & parameters.
 returns nil if it is unable to persist the data.
 returns true if successful.