function totalUnderlyingMinusSponsored() public view returns (uint256) {
    // TODO no invested amount yet
    return totalUnderlying() - totalSponsored;
}
if (_force && sponsorAmount > totalUnderlying()) {
    sponsorToTransfer = totalUnderlying();
}
function totalUnderlyingMinusSponsored() public view returns (uint256) {
    uint256 _totalUnderlying = totalUnderlying();
    if (totalSponsored > _totalUnderlying) {
        return 0;
    }
    return _totalUnderlying - totalSponsored;
}
