function _swapExactT4T() {
  // withdraw happens here
    Fund(fund()).withdraw(tokens[0], pairs[0], amounts[0]);
    _swap(amounts, pairs, tokens, fund());
}

function _swap() {
  uint256 startingBalance = IERC20(outToken).balanceOf(_to);
  uint256 endingBalance = IERC20(outToken).balanceOf(_to);
  // passes as startingBalance == endingBalance + 0
  require(
      endingBalance >= startingBalance + amounts[amounts.length - 1],
      "Defective AMM route; balances don't match"
  );
}
