import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * A simplistic collection which implements only the bare minimum allowed by the spec, and throws
 * exceptions whenever it can.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@NullMarked
public class MinimalCollection<E extends @Nullable Object> extends AbstractCollection<E> {
  // TODO: expose allow nulls parameter?

Having `str | None` will allow your editor to give you better support and detect errors.

///

## Additional validation { #additional-validation }

We are going to enforce that even though `q` is optional, whenever it is provided, **its length doesn't exceed 50 characters**.

### Import `Query` and `Annotated` { #import-query-and-annotated }

To achieve that, first import:

* `Query` from `fastapi`
* `Annotated` from `typing`

And that function takes parameters in the same way that *path operation functions* do.

/// 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.

import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * A simplistic collection which implements only the bare minimum allowed by the spec, and throws
 * exceptions whenever it can.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@NullMarked
public class MinimalCollection<E extends @Nullable Object> extends AbstractCollection<E> {
  // TODO: expose allow nulls parameter?

   *
   * <p>This differs from {@code Long.bitCount(x) == 1}, because {@code
   * Long.bitCount(Long.MIN_VALUE) == 1}, but {@link Long#MIN_VALUE} is not a power of two.
   */
  // Whenever both tests are cheap and functional, it's faster to use &, | instead of &&, ||
  @SuppressWarnings("ShortCircuitBoolean")
  public static boolean isPowerOfTwo(long x) {
    return x > 0 & (x & (x - 1)) == 0;
  }

  /**

### Extended testing file { #extended-testing-file }

You could then update `test_main.py` with the extended tests:

{* ../../docs_src/app_testing/app_b_an_py310/test_main.py *}


Whenever you need the client to pass information in the request and you don't know how to, you can search (Google) how to do it in `httpx`, or even how to do it with `requests`, as HTTPX's design is based on Requests' design.

Then the computer / program 🤖 will come back every time it has a chance because it's waiting again, or whenever it 🤖 finished all the work it had at that point. And it 🤖 will see if any of the tasks it was waiting for have already finished, doing whatever it had to do.

Next, it 🤖 takes the first task to finish (let's say, our "slow-file" 📝) and continues whatever it had to do with it.

{* ../../docs_src/body_nested_models/tutorial003_py310.py hl[12] *}

With this, even if you receive a request with duplicate data, it will be converted to a set of unique items.

And whenever you output that data, even if the source had duplicates, it will be output as a set of unique items.

And it will be annotated / documented accordingly too.

## Nested Models { #nested-models }

* Methods.
* Request payloads in the body, query parameters, etc.
* Response payloads.

You would also have **inline errors** for everything.

And whenever you update the backend code, and **regenerate** the frontend, it would have any new *path operations* available as methods, the old ones removed, and any other change would be reflected on the generated code. 🤓

#### Password hashing { #password-hashing }

"Hashing" means: converting some content (a password in this case) into a sequence of bytes (just a string) that looks like gibberish.

Whenever you pass exactly the same content (exactly the same password) you get exactly the same gibberish.

But you cannot convert from the gibberish back to the password.

##### Why use password hashing { #why-use-password-hashing }