Returns a non-null value if this response was passed to {@link Callback#onResponse} or returned
from {@link Call#execute()}. Response bodies must be {@linkplain ResponseBody closed} and may
be consumed only once.
<p>This always returns null on responses returned from {@link #cacheResponse}, {@link
#networkResponse}, and {@link #priorResponse()}.
Returns a non-null value if this response was passed to {@link Callback#onResponse} or returned from {@link Call#execute()}. Response bodies must be {@linkplain ResponseBody closed} and may be consumed only once.
<p>This always returns null on responses returned from {@link #cacheResponse}, {@link #networkResponse}, and {@link #priorResponse()}.