[Ethereum] web3.eth.personal : “Method not found”

When I invoke a method of web3.eth.personal I receive an error as follows:

> web3.eth.personal.getAccounts().then(console.log);
Promise {
  <pending>,
  domain: 
   Domain {
     domain: null,
     _events: 
      { removeListener: [Function: updateExceptionCapture],
        newListener: [Function: updateExceptionCapture],
        error: [Function: debugDomainError] },
     _eventsCount: 3,
     _maxListeners: undefined,
     members: [] } }
> (node:34481) UnhandledPromiseRejectionWarning: Error: Returned error: Method not found
    at Object.ErrorResponse (/home/s/node_modules/web3-core-helpers/src/errors.js:29:16)
    at /home/s/node_modules/web3-core-requestmanager/src/index.js:140:36
    at XMLHttpRequest.request.onreadystatechange (/home/s/node_modules/web3-providers-http/src/index.js:77:13)
    at XMLHttpRequestEventTarget.dispatchEvent (/home/s/node_modules/xhr2/lib/xhr2.js:64:18)
    at XMLHttpRequest._setReadyState (/home/s/node_modules/xhr2/lib/xhr2.js:354:12)
    at XMLHttpRequest._onHttpResponseEnd (/home/s/node_modules/xhr2/lib/xhr2.js:509:12)
    at IncomingMessage.<anonymous> (/home/s/node_modules/xhr2/lib/xhr2.js:469:24)
    at IncomingMessage.emit (events.js:185:15)
    at IncomingMessage.emit (domain.js:440:23)
    at endReadableNT (_stream_readable.js:1106:12)
    at process._tickCallback (internal/process/next_tick.js:178:19)
(node:34481) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:34481) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Do I need to install or define any additional requirements ?
Also I have installed web3-eth-personal as follows:

npm install web3-eth-personal

And then I use following commands:

var Personal = require('web3-eth-personal');
var personal = new Personal( new Personal.providers.HttpProvider("http://localhost:8545"));
web3.eth.personal.getAccounts().then(console.log);

PS. I found the solution: I started the Parity with Parity --chain tobalaba --jsonrpc-hosts all --jsonrpc-interface all --jsonrpc-cors '*' --jsonrpc-apis 'web3,eth,net,parity,traces,rpc,parity_set,personal' and now it works.