ylogenetic diversity objective finds the set of
planning units that meets representation targets for a phylogenetic tree
while staying within a fixed budget. If multiple solutions can meet all
targets while staying within budget, the cheapest solution is chosen.
Note that this objective is similar to the maximum
features objective (<code><a href="add_max_features_objective.html">add_max_features_objective()</a></code>) in that it
allows for both a budget and targets to be set for each feature. However,
unli