def exists(key, options = nil)
      policy = create_policy(options, Policy, default_read_policy)
      command = ExistsCommand.new(@cluster, policy, key)
      execute_command(command)
      command.exists
    end
def exists(key, options = nil)
      policy = create_policy(options, Policy, default_read_policy)
      command = ExistsCommand.new(@cluster, policy, key)
      execute_command(command)
      command.exists
    end
-------------------------------------------------------
 Existence-Check Operations
-------------------------------------------------------

  Determines if a record key exists.
  The policy can be used to specify timeouts.