19. The non-transitory machine readable medium of claim 13 , wherein the program further comprises a set of instructions for determining that a third list in the first column continues as a fourth list in the second column.
20. The non-transitory machine readable medium of claim 19 , wherein a relationship between a level of the first list and a level of the third list is the same as a relationship between a level of the second list and a level of the fourth list.