code: public long getUsedBytesOnTiersOrThrow(
        java.lang.String key) {
      if (key == null) { throw new java.lang.NullPointerException(); }
      java.util.Map<java.lang.String, java.lang.Long> map =
          internalGetUsedBytesOnTiers().getMap();
      if (!map.containsKey(key)) {
        throw new java.lang.IllegalArgumentException();
      }
      return map.get(key);
    }
docs: <code>map&lt;string, int64&gt; usedBytesOnTiers = 9;</code>