// stETH
    function balanceOf(address who) external override view returns (uint256) {
        return _shareBalances[who].div(_sharesPerToken);
    }
// contracts/VTVLVesting.sol
    function _createClaimUnchecked() private  hasNoClaim(_recipient) {
        // ...
        require(tokenAddress.balanceOf(address(this)) >= numTokensReservedForVesting + allocatedAmount, "INSUFFICIENT_BALANCE");
        // ...
    }

    function withdraw() hasActiveClaim(_msgSender()) external {
        // ...
        tokenAddress.safeTransfer(_msgSender(), amountRemaining);
        // ...
    }
