* Returns the leftmost, rightmost, etc. container in sub-tree. For example, if
* direction is D_LEFT, then we return the rightmost container and if direction
* is D_RIGHT, we return the leftmost container. This is because if we are
* Returns the leftmost, rightmost, etc. container in sub-tree. For example, if
* direction is D_LEFT, then we return the rightmost container and if direction
* is D_RIGHT, we return the leftmost container. This is because if we are