"recurse_downward", then all sub-trees under the branches are checked
also. if "how" is given as "recurse_upward", then "this" node and parent
nodes are checked. the "comp" parameter will be used for comparing the
"recurse_downward", then all sub-trees under the branches are checked
also. if "how" is given as "recurse_upward", then "this" node and parent
nodes are checked. the "comp" parameter will be used for comparing the