Ciphertext: `{"aead":"ChaCha20Poly1305","iv":"JbI+vwvYww1lCb5VpkAFuQ==","nonce":"ARjIjJxBSD541Gz8","bytes":"KCbEc2sA0TLvA7aWTWa23AdccVfJMpOxwgG8hm+4PaNrxYfy1xFWZg2gEenVrOgv"}`,
	},
	{
		KeyID:      "my-key",
		Plaintext:  "UnPWsZgVI+T4L9WGNzFlP1PsP1Z6hn2Fx8ISeZfDGnA=",
		Ciphertext: `{"aead":"ChaCha20Poly1305","iv":"r4+yfiVbVIYR0Z2I9Fq+6g==","nonce":"2YpwGwE59GcVraI3","bytes":"k/svMglOU7/Kgwv73heG38NWW575XLcFp3SaxQHDMjJGYyRI3Fiygu2OeutGPXNL"}`,

			return
		}
		copy(objectEncryptionKey[:], key)

		var nonce [12]byte
		tmp := sha256.Sum256(fmt.Append(nil, uploadID, partID))
		copy(nonce[:], tmp[:12])

		partEncryptionKey := objectEncryptionKey.DerivePartKey(uint32(partID))
		encReader, err := sio.EncryptReader(reader, sio.Config{
			Key:   partEncryptionKey[:],
			Nonce: &nonce,
		})
		if err != nil {

Un "**callable**" en Python es cualquier cosa que Python pueda "llamar" como una función.

Entonces, si tienes un objeto `something` (que podría _no_ ser una función) y puedes "llamarlo" (ejecutarlo) como:

```Python
something()
```

o

```Python
something(some_argument, some_keyword_argument="foo")
```

entonces es un "callable".

## Clases como dependencias { #classes-as-dependencies_1 }

##### Figure 1 - Secure Channel construction

```
plaintext   := chunk_0          ||       chunk_1          ||       chunk_2          ||       ...
                 |                         |                         |
                 |                         |                         |
               AEAD <- key, nonce + 0    AEAD <- key, nonce + 1    AEAD <- key, nonce + 2    ...

```console
$ python myapp.py
```

</div>

entonces la variable interna `__name__` en tu archivo, creada automáticamente por Python, tendrá como valor el string `"__main__"`.

Así que, la sección:

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

se ejecutará.

---

Esto no ocurrirá si importas ese módulo (archivo).

Entonces, si tienes otro archivo `importer.py` con:

```Python

	//   return len(e) > 16 && !bytes.ContainsRune(e, '-')
	//
	// An encrypted ETag may contain some random bytes - e.g.
	// and nonce value. This nonce value may contain a '-'
	// just by its nature of being randomly generated.
	// The above implementation would incorrectly consider
	// such an ETag (with a nonce value containing a '-')
	// as non-encrypted.

	return len(e) >= 32 // We consider all ETags longer than 32 bytes as encrypted
}

Para sobrescribir una dependencia para las pruebas, colocas como clave la dependencia original (una función), y como valor, tu dependencia para sobreescribir (otra función).

Y entonces **FastAPI** llamará a esa dependencia para sobreescribir en lugar de la dependencia original.

{* ../../docs_src/dependency_testing/tutorial001_an_py310.py hl[26:27,30] *}

/// tip | Consejo

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    it, and giving a relevant date.

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    released under this License and any conditions added under section
    7.  This requirement modifies the requirement in section 4 to
    "keep intact all notices".

    c) You must license the entire work, as a whole, under this

      (b) You must cause any modified files to carry prominent notices
          stating that You changed the files; and

      (c) You must retain, in the Source form of any Derivative Works
          that You distribute, all copyright, patent, trademark, and
          attribution notices from the Source form of the Work,
          excluding those notices that do not pertain to any part of
          the Derivative Works; and