//
  // - @PolyNull means "@Nullable or @Nonnull"
  //   (That would be unsound for an input Iterable<@Nullable Foo>. So, if we wanted to use
  //   @PolyNull, we would have to restrict this method to non-null <T>. But it has users who pass
  //   iterables with null elements.)
  //
  // - @JointlyNullable means "@Nullable or no annotation"

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</div>

## Forbid Extra Headers { #forbid-extra-headers }

In some special use cases (probably not very common), you might want to **restrict** the headers that you want to receive.

You can use Pydantic's model configuration to `forbid` any `extra` fields:

{* ../../docs_src/header_param_models/tutorial002_an_py310.py hl[10] *}

   * Why? We want for queries like containsKey(null) to return false, but the
   * GWT SortedMap implementation that we delegate to throws
   * NullPointerException if the comparator does. Since our construction
   * methods ensure that null is never present in the map, it's OK for the
   * comparator to look for it wherever it wants.
   *

# Stream Data { #stream-data }

If you want to stream data that can be structured as JSON, you should [Stream JSON Lines](../tutorial/stream-json-lines.md).

But if you want to **stream pure binary data** or strings, here's how you can do it.

/// info

Added in FastAPI 0.134.0.

///

## Use Cases { #use-cases }

You could use this if you want to stream pure strings, for example directly from the output of an **AI LLM** service.

versions](https://square.github.io/okhttp/5.x/okhttp/okhttp3/-tls-version/) and [cipher suites](https://square.github.io/okhttp/5.x/okhttp/okhttp3/-cipher-suite/) to offer. A client that wants to maximize connectivity would include obsolete TLS versions and weak-by-design cipher suites. A strict client that wants to maximize security would be limited to only the latest TLS version and strongest cipher suites.

Specific security vs. connectivity decisions are implemented by [ConnectionSpec...

{* ../../docs_src/path_operation_advanced_configuration/tutorial001_py310.py hl[6] *}

### Using the *path operation function* name as the operationId { #using-the-path-operation-function-name-as-the-operationid }

If you want to use your APIs' function names as `operationId`s, you can iterate over all of them and override each *path operation's* `operation_id` using their `APIRoute.name`.

You should do it after adding all your *path operations*.

	if err == io.EOF { // Verify content SHA256, if set.
		if r.expectedMin > 0 {
			if r.bytesRead < r.expectedMin {
				return 0, SizeTooSmall{Want: r.expectedMin, Got: r.bytesRead}
			}
		}
		if r.expectedMax > 0 {
			if r.bytesRead > r.expectedMax {
				return 0, SizeTooLarge{Want: r.expectedMax, Got: r.bytesRead}
			}
		}

		if r.sha256 != nil {
			if sum := r.sha256.Sum(nil); !bytes.Equal(r.contentSHA256, sum) {

///

## Forbid Extra Cookies { #forbid-extra-cookies }

In some special use cases (probably not very common), you might want to **restrict** the cookies that you want to receive.

/// tip

Do you want to understand what's all that above?

Continue reading. 👇🤓

///

## Why Virtual Environments { #why-virtual-environments }

To work with FastAPI you need to install [Python](https://www.python.org/).

After that, you would need to **install** FastAPI and any other **packages** you want to use.

	}
	expectAuthors := []string{"Edward", "George"}
	for i, post := range egPosts {
		t.Log(i, post.Author)
		if want := expectAuthors[i]; post.Author.Name != want {
			t.Errorf("expected author %s got %s", want, post.Author.Name)
		}
	}
}

func TestEmbeddedPointerTypeStruct(t *testing.T) {
	type BasePost struct {
		Id    int64
		Title string
		URL   string
	}