OZ-Crowdsale-Withdraw.sol

function withdraw() public {
  _checkWithdrawal();
  _token.safeTransfer(_wallet, _token.balanceOf(address(this)));
}

funciton _checkWithdrawal() internal {
  // This could be anything relevant. For example:
  // 1. require(now > hasClosed());
  // 2. require(isFinalized());
  // 3. require(numContributors == maxNumContributors);
}