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

### Other utility functions { #other-utility-functions }

Any other utility function that you call directly can be created with normal `def` or `async def` and FastAPI won't affect the way you call it.

This is in contrast to the functions that FastAPI calls for you: *path operation functions* and dependencies.

/**
 * Legacy version of {@link java.util.function.Function java.util.function.Function}.
 *
 * <p>The {@link Functions} class provides common functions and related utilities.
 *
 * <p>As this interface extends {@code java.util.function.Function}, an instance of this type can be
 * used as a {@code java.util.function.Function} directly. To use a {@code
 * java.util.function.Function} in a context where a {@code com.google.common.base.Function} is

            ArrayListMultimap.<String, Integer>create(), Functions.<Integer>identity())
        .asMap();
  }

  @Override
  protected Map<String, Collection<Integer>> makePopulatedMap() {
    ListMultimap<String, Integer> delegate = ArrayListMultimap.create();
    populate(delegate);
    return Multimaps.transformValues(delegate, Functions.<Integer>identity()).asMap();
  }

# Request Parameters

Here's the reference information for the request parameters.

These are the special functions that you can put in *path operation function* parameters or dependency functions with `Annotated` to get data from the request.

It includes:

* `Query()`
* `Path()`
* `Body()`
* `Cookie()`
* `Header()`
* `Form()`
* `File()`

You can import them all directly from `fastapi`:

```python

    checkArgument(!list.isEmpty(), "number of hash functions (%s) must be > 0", list.size());
    return new ConcatenatedHashFunction(list.toArray(new HashFunction[0]));
  }

  private static final class ConcatenatedHashFunction extends AbstractCompositeHashFunction {

    private ConcatenatedHashFunction(HashFunction... functions) {
      super(functions);
      for (HashFunction function : functions) {
        checkArgument(

            ArrayListMultimap.<String, Integer>create(), Functions.<Integer>identity())
        .asMap();
  }

  @Override
  protected Map<String, Collection<Integer>> makePopulatedMap() {
    ListMultimap<String, Integer> delegate = ArrayListMultimap.create();
    populate(delegate);
    return Multimaps.transformValues(delegate, Functions.<Integer>identity()).asMap();
  }

///

/// tip

If you want to call `async` functions in your tests apart from sending requests to your FastAPI application (e.g. asynchronous database functions), have a look at the [Async Tests](../advanced/async-tests.md) in the advanced tutorial.

///

## Separating tests { #separating-tests }

 * java.util.function.Function java.util.function.Function}.
 *
 * <p>The {@link Functions} class provides common functions and related utilities.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/FunctionalExplained">the use of {@code Function}</a>.
 *
 * <h3>For Java 8+ users</h3>
 *

## ty

If ty is available, use it to check types.

## Asyncer

When needing to run blocking code inside of async functions, or async code inside of blocking functions, suggest using Asyncer.

Prefer it over AnyIO or asyncio.

Install:

```bash
uv add asyncer
```

Run blocking sync code inside of async with `asyncify()`:

```python