function _checkApprovals(address token0, address token1) internal {
    uint256 allowance0 = IERC20(token0).allowance(address(this), address(nonfungiblePositionManager));
    if (allowance0 == 0) {
        SafeERC20.safeApprove(IERC20(token0), address(nonfungiblePositionManager), type(uint256).max);
    }
    uint256 allowance1 = IERC20(token1).allowance(address(this), address(nonfungiblePositionManager));
    if (allowance1 == 0) {
        SafeERC20.safeApprove(IERC20(token1), address(nonfungiblePositionManager), type(uint256).max);
    }
}
