if metadata {
		checkObjMeta = func(name string, action policy.Action) (s3Err APIErrorCode) {
			return checkRequestAuthType(ctx, r, action, bucket, name)
		}
	}
	urlValues := r.Form

	// Extract all the listBucketVersions query params to their native values.
	prefix, marker, delimiter, maxkeys, encodingType, versionIDMarker, errCode := getListBucketObjectVersionsArgs(urlValues)
	if errCode != ErrNone {

				"Content-Type": []string{"image/png"},
			},
			metadata: map[string]string{
				"content-type": "image/png",
			},
			shouldFail: false,
		},
		// Validate if there are no keys to extract.
		{
			header: http.Header{
				"Test-1": []string{"123"},
			},
			metadata:   map[string]string{},
			shouldFail: false,
		},
		// Validate that there are all headers extracted
		{

 * be used to decide whether to apply a test to a given class-under-test.
 *
 * <p>This is needed because annotations can't implement interfaces, which is also why reflection is
 * used to extract values from the properties of the various annotations.
 *
 * @author George van den Driessche
 */
@Target(value = {ElementType.ANNOTATION_TYPE})
@Retention(value = RetentionPolicy.RUNTIME)
@Documented
@GwtCompatible

    }

    /**
     * Gets a typed value from a document map with a default value.
     *
     * @param <T> the type to convert the value to
     * @param doc the document map to extract the value from
     * @param key the key to look up in the document map
     * @param clazz the class type to convert the value to
     * @param defaultValue the default value to return if the key is not found or conversion fails

	// Simplify the work of url.Parse() and always send a url with
	if !strings.HasPrefix(hostAddr, "http://") && !strings.HasPrefix(hostAddr, "https://") {
		hostAddr = "//" + hostAddr
	}

	// Parse address to extract host and scheme field
	u, err := url.Parse(hostAddr)
	if err != nil {
		return "", "", err
	}

	addr = u.Host
	scheme = u.Scheme

	// Use the given parameter again if url.Parse()

	if err != ErrNone {
		return err
	}

	// Extract all the signed headers along with its values.
	extractedSignedHeaders, errCode := extractSignedHeaders(signV4Values.SignedHeaders, r)
	if errCode != ErrNone {
		return errCode
	}

	cred, _, s3Err := checkKeyValid(r, signV4Values.Credential.accessKey)
	if s3Err != ErrNone {
		return s3Err
	}

	// Extract date, if not present throw error.
	var date string

}

func extractMetadata(ctx context.Context, mimesHeader ...textproto.MIMEHeader) (metadata map[string]string, err error) {
	metadata = make(map[string]string)

	for _, hdr := range mimesHeader {
		// Extract all query values.
		err = extractMetadataFromMime(ctx, hdr, metadata)
		if err != nil {
			return nil, err
		}
	}

	// Set content-type to default value if it is not set.

 * certificate.
 *
 * Use of the chain cleaner is necessary to omit unexpected certificates that aren't relevant to
 * the TLS handshake and to extract the trusted CA certificate for the benefit of certificate
 * pinning.
 */
abstract class CertificateChainCleaner {
  @Throws(SSLPeerUnverifiedException::class)
  abstract fun clean(
    chain: List<Certificate>,

        """
        elt = self.element.find('sts:{}'.format(name), _STS_NS)
        return STSElement(self.root_name, elt) if elt is not None else None

    def get_child_text(self, name, strict=True):
        """Extract text of a child element. If strict, and child element is
        not present, raises InvalidXMLError and otherwise returns
        None.

        """
        if strict:
            try:

But a variable like `user-agent` is invalid in Python.

So, by default, `Header` will convert the parameter names characters from underscore (`_`) to hyphen (`-`) to extract and document the headers.

Also, HTTP headers are case-insensitive, so, you can declare them with standard Python style (also known as "snake_case").