what does this piece of code doing? ```/*
    @notice withdraw position NFT to user
    */
    function withdrawV3PositionNft(
        address token0,
        address token1,
        uint24 poolFee,
        uint256 nftId
    ) external {
        require(!_depositStatus());
        //delete nft form mapping
        v3PositionNft[msg.sender][token0][token1][poolFee] = 0;
        address poolAddress = s7Read.getV3PoolAddress(token0, token1, poolFee);
        //we use the proxy map to gatekeep the rightful nft owner
        S7Proxy(userPoolProxy[msg.sender][poolAddress]).withdrawV3Nft(nftId);
    }```