Unknown option for ${key} error while doing node start.js in ds-server

[rajudev]

node start.js 
/home/raju/dev/github.com/ds-tutorial-tanks/ds-server/node_modules/deepstream.io/src/deepstream.io.js:89
      throw new Error(`Unknown option "${key}"`)
      ^

Error: Unknown option "host"
    at Deepstream.set (/home/raju/dev/github.com/ds-tutorial-tanks/ds-server/node_modules/deepstream.io/src/deepstream.io.js:89:13)
    at Object.<anonymous> (/home/raju/dev/github.com/ds-tutorial-tanks/ds-server/start.js:5:12)
    at Module._compile (module.js:569:30)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:503:32)
    at tryModuleLoad (module.js:466:12)
    at Function.Module._load (module.js:458:3)
    at Function.Module.runMain (module.js:605:10)
    at startup (bootstrap_node.js:158:16)
    at bootstrap_node.js:575:3
┌─[✗]─[raju@TBS60]─[~/dev/github.com/ds-tutorial-tanks/ds-server]
└──╼ $