extractTrait function

extractTrait(Taxa taxa, String sep, Integer i, String name)

return a trait alignment, which contains the set of traits extracted from taxa names.

Taxa taxa - the set of taxa whose names contain the traits.
String sep - the substring to split the taxa names, where Java regular expression escape characters will be given no special meaning.
Integer i - i (>=0) is the index to extract the trait value.
String name - (optional) the map containing optional arguments and their values for reuse.