Iterable<? extends R> rowKeys, Iterable<? extends C> columnKeys) {
    return new ArrayTable<>(rowKeys, columnKeys);
  }

  /*
   * TODO(jlevy): Add factory methods taking an Enum class, instead of an
   * iterable, to specify the allowed row keys and/or column keys. Note that
   * custom serialization logic is needed to support different enum sizes during
   * serialization and deserialization.

      Iterable<? extends R> rowKeys, Iterable<? extends C> columnKeys) {
    return new ArrayTable<>(rowKeys, columnKeys);
  }

  /*
   * TODO(jlevy): Add factory methods taking an Enum class, instead of an
   * iterable, to specify the allowed row keys and/or column keys. Note that
   * custom serialization logic is needed to support different enum sizes during
   * serialization and deserialization.