def ladderize(self, direction=<NUM_LIT:0>):
nself = deepcopy(self)<EOL>nself.treenode.ladderize(direction=direction)<EOL>nself._fixed_order = None<EOL>nself._coords.update()<EOL>return nself<EOL>
Ladderize tree (order descendants) so that top child has fewer 
descendants than the bottom child in a left to right tree plot. 
To reverse this pattern use direction=1.