Do not rely on `@NullMarked` annotations.
Only enable checks for a project if all its dependencies have checks enabled, in order to avoid back-and-forth when refining the annotations.

Avoid writing the so-called `PolyNull` or `ParametricNull` methods (where nullability of the result depends on the nullability of the type argument).

The key factor is that a dependency should be a "callable".

A "**callable**" in Python is anything that Python can "call" like a function.

So, if you have an object `something` (that might _not_ be a function) and you can "call" it (execute it) like:

```Python
something()
```

or

```Python
something(some_argument, some_keyword_argument="foo")

in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

import java.util.concurrent.TimeUnit.SECONDS
import okhttp3.MediaType
import okhttp3.RequestBody
import okio.BufferedSink
import org.junit.jupiter.api.Assertions.assertTrue

/** A duplex request body that keeps the provided sinks so they can be written to later.  */
class AsyncRequestBody : RequestBody() {
  private val requestBodySinks: BlockingQueue<BufferedSink> = LinkedBlockingQueue()

  override fun contentType(): MediaType? = null

   * executor promptly, or else the returned {@code ListenableFuture} may fail to work. The task's
   * execution consists of blocking until the input future is {@linkplain Future#isDone() done}, so
   * each call to this method may claim and hold a thread for an arbitrary length of time. Use of
   * bounded executors or other executors that may fail to execute a task promptly may result in
   * deadlocks.
   *

      </plugin>
      <plugin>
        <artifactId>maven-javadoc-plugin</artifactId>
        <configuration>
          <!-- Passing `-subpackages com.google.common` breaks things, so we explicitly exclude everything else instead. -->
          <!-- excludePackageNames requires specification of packages separately from "all subpackages".
               https://issues.apache.org/jira/browse/MJAVADOC-584 -->

            // so even if they were all nonnull, we wouldn't detect a hash flood.  Therefore,
            // we can skip them all.
            knownRunStart += maxRunBeforeFallback;
          } else {
            knownRunStart++; // the only case in which maxRunEnd doesn't increase by mRBF
            // happens about f * (1-f) for f = DESIRED_LOAD_FACTOR, so around 21% of the time
          }

      // If toTrickle is moved up to a parent of removeIndex, the parent is
      // placed in removeIndex position. We must return that to the iterator so
      // that it knows to skip it.
      if (crossOver < removeIndex) {
        // We crossed over to the parent level in crossOver, so the parent
        // has already been moved.
        parent = elementData(removeIndex);
      } else {