```\\nfunction _withdrawERC20(address account, ERC20 token)\\n  internal\\n  returns (uint256 withdrawn)\\n{\\n  // leave balance of 1 for gas efficiency\\n  // underflow if erc20Balance is 0\\n  withdrawn = erc20Balances[token][account] - 1;\\n  erc20Balances[token][account] = 1;\\n  token.safeTransfer(account, withdrawn);\\n}\\n```\\n