     A -- B -- C -- D(latest confirmed) -- E
     A -- B -- C -- D(latest confirmed) -- E
                                        \
                                         \ F(invalid)
            if (!getAssertionStorage(newAssertionHash).isFirstChild) {

                // only 1 of the children can be confirmed and get their stake refunded
                // so we send the other children's stake to the loserStakeEscrow
                IERC20(stakeToken).safeTransfer(loserStakeEscrow, assertion.beforeStateData.configData.requiredStake);
            }
     A -- B -- C -- D(latest confirmed) -- E
                                        \

                                         \ F -- G
            // requiredStake is user supplied, will be verified against configHash later
            // the prev's requiredStake is used to make sure all children have the same stake
            // the staker may have more than enough stake, and the entire stake will be locked
            // we cannot do a refund here because the staker may be staker on an unconfirmed ancestor that requires more stake
            // excess stake can be removed by calling reduceDeposit when the staker is inactive
            require(amountStaked(msg.sender) >= assertion.beforeStateData.configData.requiredStake, "INSUFFICIENT_STAKE");
        function requireInactiveStaker(address stakerAddress) internal view {
            require(isStaked(stakerAddress), "NOT_STAKED");
            // A staker is inactive if
            // a) their last staked assertion is the latest confirmed assertion
            // b) their last staked assertion have a child
            bytes32 lastestAssertion = latestStakedAssertion(stakerAddress);
            bool isLatestConfirmed = lastestAssertion == latestConfirmed();
            bool haveChild = getAssertionStorage(lastestAssertion).firstChildBlock > 0;
            require(isLatestConfirmed || haveChild, "STAKE_ACTIVE");
        }
