// and other runtime functions while identifying leaks.
var ignoredStackFns = []string{
	"",
	// Below are the stacks ignored by the upstream leaktest code.
	"testing.Main(",
	"testing.tRunner(",
	"testing.tRunner(",
	"runtime.goexit",
	"created by runtime.gc",
	// ignore the snapshot function.
	// since the snapshot is taken here the entry will have the current function too.

import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.function.Predicate;

/**
 * This should be removed when https://bugs.openjdk.org/browse/JDK-8323729
 * is released in our minimum JDK.
 */
class ImmutableCollections {

Primero, importa `BackgroundTasks` y define un parámetro en tu *path operation function* con una declaración de tipo de `BackgroundTasks`:

{* ../../docs_src/background_tasks/tutorial001_py39.py hl[1,13] *}

**FastAPI** creará el objeto de tipo `BackgroundTasks` por ti y lo pasará como ese parámetro.

## Crear una función de tarea { #create-a-task-function }

Crea una función para que se ejecute como la tarea en segundo plano.

* `"function"`: startet die Abhängigkeit vor der *Pfadoperation-Funktion*, die den Request bearbeitet, beendet die Abhängigkeit nach dem Ende der *Pfadoperation-Funktion*, aber **bevor** die Response an den Client zurückgesendet wird. Die Abhängigkeitsfunktion wird also **um** die *Pfadoperation-**Funktion*** **herum** ausgeführt.

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.concurrent.atomic.AtomicLongArray;
import java.util.function.DoubleBinaryOperator;
import java.util.function.DoubleUnaryOperator;

/**
 * A {@code double} array in which elements may be updated atomically. See the {@link

  // it in this context.
  virtual AbstractOperation* CreateOperation() = 0;

  // Registers a function with this context, after this the function is
  // available to be called/referenced by its name in this context.
  virtual absl::Status RegisterFunction(AbstractFunction*) = 0;
  // Remove a function. 'func' argument is the name of a previously added
  // FunctionDef. The name is in fdef.signature.name.

      return delegate;
    }
  }

  private static String encode(String str) {
    return BaseEncoding.base64().encode(str.getBytes(UTF_8));
  }

  private static final Function<String, String> DECODE_FUNCTION =
      new Function<String, String>() {
        @Override
        public String apply(String input) {
          return new String(BaseEncoding.base64().decode(input), UTF_8);
        }
      };

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import java.util.HashMap;
import java.util.Map;
import org.jspecify.annotations.NullMarked;

/**
 * Tests for {@link Maps#transformValues(Map, Function)}.
 *
 * @author Isaac Shum
 */
@GwtCompatible
@NullMarked

///

## Create a middleware { #create-a-middleware }

To create a middleware you use the decorator `@app.middleware("http")` on top of a function.

The middleware function receives:

* The `request`.
* A function `call_next` that will receive the `request` as a parameter.
    * This function will pass the `request` to the corresponding *path operation*.
    * Then it returns the `response` generated by the corresponding *path operation*.

import static com.google.common.truth.Truth.assertThat;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.collect.testing.MapInterfaceTest;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;