*
   * - allocArrays() has been called. Callers can confirm this by checking needsAllocArrays().
   *
   * - The map has not switched to delegating to a java.util implementation to mitigate hash
   *   flooding. Callers can confirm this by null-checking delegateOrNull().
   *
   * In an ideal world, we would document why we know those things are true every time we call these

## Version 5.1.0

_2025-07-07_

 *  New: `Response.peekTrailers()`. When we changed `Response.trailers()` to block instead of
    throwing in 5.0.0, we inadvertently removed the ability for callers to peek the trailers
    (by catching the `IllegalStateException` if they weren't available). This new API restores that
    capability.

 *  Fix: Don't crash on `trailers()` if the response doesn't have a body. We broke [Retrofit] users

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 *     http://www.apache.org/licenses/LICENSE-2.0
 *
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