code: function validateInput(params, cb) {
  	if (typeof params !== 'object')
  		return new TypeError("params must be an object");
  	if (typeof cb !== 'function')
  		return new TypeError("callback must be a function");
  	if (params.origin === "")
  		return new Error("params.origin is required");
  	if (params.destination === "")
  		return new Error("params.destination is required");
  	if (params.key === "")
  		return new Error("params.key is required");
  }
docs: validation of input