OpenZeppelin ERC20 token with changeable name/symbol

TokenWithNameSymbolChange.sol

pragma solidity ^0.5.0;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.3.0/contracts/token/ERC20/ERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.3.0/contracts/token/ERC20/ERC20Detailed.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.3.0/contracts/ownership/Ownable.sol";

contract Token is ERC20, ERC20Detailed, Ownable {

    string private _name = "DAOMaker Token";
    string private _symbol = "DAO";
    uint constant _numTokens = 1000000;
    
    event NameChanged(string newName, address by);
    event SymbolChanged(string newSymbol, address by);

    constructor () public ERC20Detailed(_name, _symbol, 18) {
        _mint(msg.sender, _numTokens * (10 ** uint256(decimals())));
    }
    
    function changeName(string memory name) public onlyOwner{
        _name = name;
        emit NameChanged(name, msg.sender);
    }
    
    function name() public view returns (string memory) {
        return _name;
    }
    
    function changeSymbol(string memory symbol) public onlyOwner {
        _symbol = symbol;
        emit SymbolChanged(symbol, msg.sender);
    }
    
    function symbol() public view returns (string memory) {
        return _symbol;
    }
}