code: String getPatternInPast(
          PluralCategory category,
          boolean abbreviated,
          IsoUnit unit
      ) {
  
          checkNull(category);
  
          if (abbreviated) {
              return this.shortPast.get(unit).get(category);
          } else {
              return this.past.get(unit).get(category);
          }
  
      }
docs: <p>Yields a unit pattern which optionally contains a placeholder
  of the form &quot;{0}&quot; standing for the count of units in the
  past. </p>
  
  @param   category        plural category
  @param   abbreviated     using short form or not
  @param   unit            associated iso unit
  @return  unit pattern in the past
  @since   3.6/4.4