addTags
fun <T : U, U : Taggable<U>, X : Any> T.addTags(tag: Pair<String, X>, vararg otherTags: Pair<String, X>): T
Returns a new instance, otherwise equivalent to this one, with tag (and any otherTags) merged into its existing Taggable.tags (overwriting any existing tags with the same names).
Returns a new instance, otherwise equivalent to this one, with tags merged into its existing Taggable.tags (overwriting any existing tags with the same names as one of tags' keys).