The replacement method taxon_relations<- should be only used when
constructing taxlist objects from an empty one
(prototype).
New concepts should be first added to a taxlist object
using their respective accepted names.
Synonyms can be further provided using the function add_synonym().
Additional named vectors can be provided to be included in slot taxonNames,
in the cases where those variables already exist, otherwise they will be
ignored.
It is recommended also to provide a concept view as ViewID (see
taxon_views()).
For adding a new view, use add_view().