code: @SuppressWarnings("unchecked")
    public Query reverseOrderBy(String key) {
      checkNotEmpty(key, "Key to order by must not be empty");
  
      if (key.startsWith("fields.") && !hasContentTypeSet()) {
        throw new IllegalStateException("\"fields.\" cannot be used without setting a content type "
            + "first.");
      }
  
      this.params.put(PARAMETER_ORDER, "-" + key);
      return (Query) this;
    }
docs: Order result by the given key, reversing the order.
  <p>
  Please do not forget to include the content type if you are requesting to order
  by a field.
  
  @param key the key to be reversely ordered by.
  @return the calling query for chaining.
  @throws IllegalArgumentException if key is null.
  @throws IllegalArgumentException if key is empty.
  @throws IllegalStateException    if key requests a field, but no content type is requested.
  @see #withContentType(String)