exampleLevels: Display a sample node from each level of a ChrBandTree object
Description
The "levels" of a chromosome band tree represented by a ChrBandTree object
are the sets of nodes with a given path length to the root node. This
function displays the available levels along with an example node from
each level.
Value
A list with an element for each level. The names of the list are the
levels. Each element is an example of a node from the given level.