code: public static Summary create(@Nullable Long count, @Nullable Double sum, Snapshot snapshot) {
      checkCountAndSum(count, sum);
      Utils.checkNotNull(snapshot, "snapshot");
      return new AutoValue_Summary(count, sum, snapshot);
    }
docs: Creates a {@link Summary}.
  
  @param count the count of the population values.
  @param sum the sum of the population values.
  @param snapshot bucket boundaries of a histogram.
  @return a {@code Summary} with the given values.
  @since 0.17