Parent nodes: Only those parent nodes are shown which meet the filtering criteria or are parent to children that meet the filtering criteria.
Children nodes: By default only those children nodes are shown which meet the filtering criteria.
treeModel.filterShowChildren is set to true, all the children of parents which meet filtering criteria
are also shown.
Summary values: By default summary values are recalculated depending upon displayed nodes in relation to filtering state.
treeModel.filterLockSummary is set to true, summary values of pre-filtered state are retained
and are not affected by filtering.