contract ERC20Mintable is ERC20, Operatorable {
    /**
     * @dev Overload _mint to ensure only operator or system can mint funds.
     * @param account address that will recieve new funds.
     * @param amount of funds to be minted.
     */
    function _mint(address account, uint256 amount) internal onlyOperatorOrSystem {
        require(amount > 0, "ERC20Mintable: amount has to be greater than 0");
        super._mint(account, amount);
    }
}
function _mint(address account, uint256 amount) internal onlyOperatorOrSystem {
    require(amount > 0, "ERC20Mintable: amount has to be greater than 0");
    super._mint(account, amount);
}

/**
 * @dev Overload _mint to ensure only operator or system can mint funds.
 * @param account address that will recieve new funds.
 * @param amount of funds to be minted.
 */