`FastAPI` es una clase que hereda directamente de `Starlette`.

    También puedes usar toda la funcionalidad de <a href="https://www.starlette.io/" class="external-link" target="_blank">Starlette</a>.

### Paso 2: crea un "instance" de `FastAPI`

```Python hl_lines="3"
{!../../../docs_src/first_steps/tutorial001.py!}
```

Aquí la variable `app` será un instance de la clase `FastAPI`.

}

func (cred Credentials) String() string {
	var s strings.Builder
	s.WriteString(cred.AccessKey)
	s.WriteString(":")
	s.WriteString(cred.SecretKey)
	if cred.SessionToken != "" {
		s.WriteString("\n")
		s.WriteString(cred.SessionToken)
	}
	if !cred.Expiration.IsZero() && !cred.Expiration.Equal(timeSentinel) {
		s.WriteString("\n")
		s.WriteString(cred.Expiration.String())
	}

	s3Err = authenticateRequest(ctx, r, action)
	reqInfo := logger.GetReqInfo(ctx)
	if reqInfo == nil {
		return cred, owner, ErrAccessDenied
	}

	cred = reqInfo.Cred
	owner = reqInfo.Owner
	if s3Err != ErrNone {
		return cred, owner, s3Err
	}

	return cred, owner, authorizeRequest(ctx, r, action)
}

	if s3Err != ErrNone {
		return auth.Credentials{}, s3Err
	}

	r := &http.Request{Header: formValues}
	cred, _, s3Err := checkKeyValid(r, credHeader.accessKey)
	if s3Err != ErrNone {
		return cred, s3Err
	}

	// Get signing key.
	signingKey := getSigningKey(cred.SecretKey, credHeader.scope.date, credHeader.scope.region, serviceS3)

	// Get signature.

func mustNewSignedRequest(method string, urlStr string, contentLength int64, body io.ReadSeeker, t *testing.T) *http.Request {
	req := mustNewRequest(method, urlStr, contentLength, body, t)
	cred := globalActiveCred
	if err := signRequestV4(req, cred.AccessKey, cred.SecretKey); err != nil {
		t.Fatalf("Unable to initialized new signed http request %s", err)
	}
	return req
}

// This is similar to mustNewRequest but additionally the request

	// Find the user for the request sender (as it may be sent via a service
	// account or STS account):
	requestorUser := cred.AccessKey
	requestorParentUser := cred.AccessKey
	requestorGroups := cred.Groups
	requestorIsDerivedCredential := false
	if cred.IsServiceAccount() || cred.IsTemp() {
		requestorParentUser = cred.ParentUser
		requestorIsDerivedCredential = true
	}

	// Check if we are creating svc account for request sender.

	extractedSignedHeaders, errCode := extractSignedHeaders(signV4Values.SignedHeaders, r)
	if errCode != ErrNone {
		return cred, "", "", time.Time{}, errCode
	}

	cred, _, errCode = checkKeyValid(r, signV4Values.Credential.accessKey)
	if errCode != ErrNone {
		return cred, "", "", time.Time{}, errCode
	}

	// Verify if region is valid.
	region = signV4Values.Credential.scope.region

	r := &http.Request{Header: formValues}
	cred, _, s3Err := checkKeyValid(r, accessKey)
	if s3Err != ErrNone {
		return cred, s3Err
	}
	policy := formValues.Get("Policy")
	signature := formValues.Get(xhttp.AmzSignatureV2)
	if !compareSignatureV2(signature, calculateSignatureV2(policy, cred.SecretKey)) {
		return cred, ErrSignatureDoesNotMatch
	}
	return cred, ErrNone
}

//	LFADD freg ',' freg
//	{
//		outcode(int($1), &$2, 0, &$4);
//	}
	ADDD	F1, F2

//	LFADD freg ',' freg ',' freg
//	{
//		outcode(int($1), &$2, int($4.Reg), &$6);
//	}
	ADDD	F1, F2, F3

//	LFCMP freg ',' freg
//	{
//		outcode(int($1), &$2, 0, &$4);
//	}
	CMPEQD	F1, F2


//
// WORD
//
	WORD	$1	// 00000001
	NOOP		// 00000000
	SYNC		// 0000000f

//

		STSCredential: &madmin.SRSTSCredential{
			AccessKey:    cred.AccessKey,
			SecretKey:    cred.SecretKey,
			SessionToken: cred.SessionToken,
			ParentUser:   cred.ParentUser,
		},
		UpdatedAt: updatedAt,
	}))

	ldapIdentityResponse := &AssumeRoleWithLDAPResponse{
		Result: LDAPIdentityResult{
			Credentials: cred,
		},
	}