function SkillChainPrivateSale(
        uint256 _startTime,
        uint256 _endTime,
        uint256 _rate,
        address _wallet,
        uint256 _cap
    )
    CappedCrowdsale(_cap)
    Crowdsale(_startTime, _endTime, _rate, _wallet)
    public
    {
        contributions = new SkillChainContributions();
    }