import java.util.Comparator;
import java.util.SortedSet;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A sorted set multimap which forwards all its method calls to another sorted set multimap.
 * Subclasses should override one or more methods to modify the behavior of the backing multimap as
 * desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *

import com.google.common.base.Preconditions;
import java.util.concurrent.Executor;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link ListenableFuture} which forwards all its method calls to another future. Subclasses
 * should override one or more methods to modify the behavior of the backing future as desired per
 * the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *

   *
   * @param formal The type whose type variables or itself is mapped to other type(s). It's almost
   *     always a bug if {@code formal} isn't a type variable and contains no type variable. Make
   *     sure you are passing the two parameters in the right order.
   * @param actual The type that the formal type variable(s) are mapped to. It can be or contain yet
   *     other type variables, in which case these type variables will be further resolved if

```Python hl_lines="3  6-8"
{!../../docs_src/sub_applications/tutorial001.py!}
```

### Sub-application

Then, create your sub-application, and its *path operations*.

This sub-application is just another standard FastAPI application, but this is the one that will be "mounted":

```Python hl_lines="11  14-16"
{!../../docs_src/sub_applications/tutorial001.py!}
```

### Mount the sub-application

To override a dependency for testing, you put as a key the original dependency (a function), and as the value, your dependency override (another function).

And then **FastAPI** will call that override instead of the original dependency.

//// tab | Python 3.10+

```Python hl_lines="26-27  30"
{!> ../../docs_src/dependency_testing/tutorial001_an_py310.py!}

import org.apache.maven.model.building.ModelProblemCollector;
import org.apache.maven.model.building.ModelProblemCollectorRequest;
import org.codehaus.plexus.interpolation.ValueSource;

/**
 * Wraps another value source and intercepts interpolated expressions, checking for problems.
 *
 * @deprecated use {@link org.apache.maven.api.services.ModelBuilder} instead
 */
@Deprecated(since = "4.0.0")

import java.util.Comparator;
import java.util.SortedSet;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A sorted set multimap which forwards all its method calls to another sorted set multimap.
 * Subclasses should override one or more methods to modify the behavior of the backing multimap as
 * desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *

 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public final class CountingInputStream extends FilterInputStream {

  private long count;
  private long mark = -1;

  /**
   * Wraps another input stream, counting the number of bytes read.
   *
   * @param in the input stream to be wrapped
   */
  public CountingInputStream(InputStream in) {
    super(checkNotNull(in));
  }

          return null
        }
        val priorResponse = userResponse.priorResponse
        if (priorResponse != null && priorResponse.code == HTTP_CLIENT_TIMEOUT) {
          // We attempted to retry and got another timeout. Give up.
          return null
        }

        if (retryAfter(userResponse, 0) > 0) {
          return null
        }

        return userResponse.request
      }

  @GuardedBy("queue")
  private WorkerRunningState workerRunningState = IDLE;

  /**
   * This counter prevents an ABA issue where a thread may successfully schedule the worker, the
   * worker runs and exhausts the queue, another thread enqueues a task and fails to schedule the
   * worker, and then the first thread's call to delegate.execute() returns. Without this counter,