Rows that correspond to items in the root model have a depth
of zero, rows corresponding to items of models of direct children
of the root model have a depth of 1 and so on.
The depth of a row never changes until the row is removed from its model
at which point it will forever return 0.
Gets the depth of this row.
Rows that correspond to items in the root model have a depth of zero, rows corresponding to items of models of direct children of the root model have a depth of 1 and so on.
The depth of a row never changes until the row is removed from its model at which point it will forever return 0.