code: public ExternalID getSeasonExternalID(int tvID, int seasonNumber, String language) throws MovieDbException {
          return tmdbSeasons.getSeasonExternalID(tvID, seasonNumber, language);
      }
docs: Get the external ids that we have stored for a TV season by season
  number.
  
  @param tvID tvID
  @param seasonNumber seasonNumber
  @param language language
  @return
  @throws MovieDbException exception