FinalizableReference.register(this);
  }

  /**
   * Returns a future that finishes when this step does. Calling {@code get()} on the returned
   * future returns {@code null} if the step is successful or throws the same exception that would
   * be thrown by calling {@code finishToFuture().get()} if this were the last step. Calling {@code
   * cancel()} on the returned future has no effect on the {@code ClosingFuture} pipeline.
   *

     * LF<? extends @Nullable V>. That might be better: There's currently no difference between the
     * outputs users get when calling this with <Foo> and calling it with <@Nullable Foo>. The only
     * difference is that calling it with <Foo> won't work when an input Future has a @Nullable
     * type. So why even make that error possible by giving callers the choice?
     *

But **FastAPI** will know that it has to solve `query_extractor` first, to pass the results of that to `query_or_cookie_extractor` while calling it.

///

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

  /**
   * Any interruption that happens as a result of calling interruptTask will arrive before this
   * method is called. Complete Futures here.
   */
  abstract void afterRanInterruptiblySuccess(@ParametricNullness T result);

  /**
   * Any interruption that happens as a result of calling interruptTask will arrive before this
   * method is called. Complete Futures here.
   */

   * in a {@code RuntimeException}. <b>Note:</b> Be sure to declare all of the checked exception
   * types your try block can throw when calling an overload of this method so as to avoid losing
   * the original exception type.
   *
   * <p>This method always throws, and as such should be called as {@code throw closer.rethrow(e);}

/// tip

You'll see what other "things", apart from functions, can be used as dependencies in the next chapter.

///

Whenever a new request arrives, **FastAPI** will take care of:

* Calling your dependency ("dependable") function with the correct parameters.
* Get the result from your function.
* Assign that result to the parameter in your *path operation function*.

```mermaid
graph TB

import okio.Options
import okio.Source
import okio.Timeout
import okio.buffer

/**
 * Reads a stream of [RFC 2046][rfc_2046] multipart body parts. Callers read parts one-at-a-time
 * until [nextPart] returns null. After calling [nextPart] any preceding parts should not be read.
 *
 * Typical use loops over the parts in sequence:
 *
 * ```kotlin
 * val response: Response = call.execute()
 * val multipartReader = MultipartReader(response.body!!)

   * note that the execution order of all listeners is ultimately chosen by the implementations of
   * the supplied executors.
   *
   * <p>This method is idempotent. Calling it several times in parallel is semantically equivalent
   * to calling it exactly once.
   *
   * @since 10.0 (present in 1.0 as {@code run})
   */
  public void execute() {

            copySpec.rename(s -> destinationFile.getName());

            // TODO: Maybe this could be simplified by not using the copy infrastructure and just
            // calling the FilterReader ourselves.  We're just taking one file and turning it into another.

            // The order here is important! tokens are inserted by the transformer
            Map<String, Object> parameters = new HashMap<>();

	ErrNegativeCount     = errors.New("bufio: negative count")
)

// Buffered input.

// Reader implements buffering for an io.Reader object.
// A new Reader is created by calling [NewReader] or [NewReaderSize];
// alternatively the zero value of a Reader may be used after calling [Reader.Reset]
// on it.
type Reader struct {
	buf          []byte
	rd           io.Reader // reader provided by the client