Django - counting 'depth' of 'select_related' to get know how many nodes has object to top object -

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for example if have model class this:

class category(models.model)     parent = models.manytomanyfield('self', symmetrical=false, blank=true)

and have instance of category have parent parent has albo has parent, there possibility value of children instance top category? , there possibility count somehow depth of deepest related object of of category instance?

if need trees of model instances, take @ django-mptt or django-treebeard. both provide lot of convenience.


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