code: public void addIfAbsent(CharSequence variant, String template) {
          int idx = StandardPlural.indexFromString(variant);
          if (templates[idx] != null) {
              return;
          }
          templates[idx] = SimpleFormatter.compileMinMaxArguments(template, 0, 1);
      }
docs: Adds a template if there is none yet for the plural form.
  
  @param variant the plural variant, e.g "zero", "one", "two", "few", "many", "other"
  @param template the text for that plural variant with "{0}" as the quantity. For
  example, in English, the template for the "one" variant may be "{0} apple" while the
  template for the "other" variant may be "{0} apples"
  @throws IllegalArgumentException if variant is not recognized or
  if template has more than just the {0} placeholder.