# Development - Contributing

First, you might want to see the basic ways to [help FastAPI and get help](help-fastapi.md){.internal-link target=_blank}.

## Developing

If you already cloned the <a href="https://github.com/fastapi/fastapi" class="external-link" target="_blank">fastapi repository</a> and you want to deep dive in the code, here are some guidelines to set up your environment.

### Virtual environment

	}
	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
	}

<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] *}

func bitrotVerify(r io.Reader, wantSize, partSize int64, algo BitrotAlgorithm, want []byte, shardSize int64) error {
	if algo != HighwayHash256S {
		h := algo.New()
		if n, err := io.Copy(h, r); err != nil || n != wantSize {
			// Premature failure in reading the object, file is corrupt.
			return errFileCorrupt
		}
		if !bytes.Equal(h.Sum(nil), want) {
			return errFileCorrupt
		}
		return nil
	}

 * This is only necessary for default components using @Typed that want to support overriding.
 *
 * As a non-default component this now gets a negative priority relative to other implementations
 * of the same interface. Since we want to allow overriding this doesn't matter in this case.
 * (if it did we could add @Priority of 0 to match the priority given to default components.)
 *

      @ParametricNullness E fromElement,
      BoundType fromBoundType,
      @ParametricNullness E toElement,
      BoundType toBoundType) {
    // These are checked elsewhere, but NullPointerTester wants them checked eagerly.
    checkNotNull(fromBoundType);
    checkNotNull(toBoundType);
    return tailMultiset(fromElement, fromBoundType).headMultiset(toElement, toBoundType);
  }

You can import it directly from `fastapi`:

```python
from fastapi import Request
```

/// tip

When you want to define dependencies that should be compatible with both HTTP and WebSockets, you can define a parameter that takes an `HTTPConnection` instead of a `Request` or a `WebSocket`.

///

		version string
		format  string
		want    bool
	}{
		{1, "123", "fs", false},
		{2, "123", xlMetaFormat, false},
		{3, xlMetaVersion100, "test", false},
		{4, xlMetaVersion101, "hello", false},
		{5, xlMetaVersion100, xlMetaFormat, true},
		{6, xlMetaVersion101, xlMetaFormat, true},
	}
	for _, tt := range tests {
		if got := isXLMetaFormatValid(tt.version, tt.format); got != tt.want {

# `HTTPConnection` class

When you want to define dependencies that should be compatible with both HTTP and WebSockets, you can define a parameter that takes an `HTTPConnection` instead of a `Request` or a `WebSocket`.

You can import it from `fastapi.requests`:

```python
from fastapi.requests import HTTPConnection
```

And you could have a single dependency that requires several other dependencies with `yield`, etc.

You can have any combinations of dependencies that you want.

**FastAPI** will make sure everything is run in the correct order.

/// note | Technical Details