// way for it to return a false negative would be for the target value to jump around in the map
    // such that none of the subsequent iterations observed it, despite the fact that at every point
    // in time it was present somewhere int the map. This becomes increasingly unlikely as
    // CONTAINS_VALUE_RETRIES increases, though without locking it is theoretically possible.

   * X> if we support such a thing? It would be weird or misleading for users to be able to pass
   * `new TypeParameter<@Nullable T>() {}` and have it act as a plain `TypeParameter<T>`, but
   * hopefully no one would do that, anyway. See also the comment on TypeParameter itself.
   *
   * TODO(cpovirk): Elaborate on this / merge with other comment?
   */