How to use the onelogin.saml2.xml_utils.OneLogin_Saml2_XML.to_etree function in onelogin

"""
        Decrypts an encrypted element.

        :param encrypted_data: The encrypted data.
        :type: lxml.etree.Element | DOMElement | basestring

        :param key: The key.
        :type: string

        :param debug: Activate the xmlsec debug
        :type: bool

        :returns: The decrypted element.
        :rtype: lxml.etree.Element
        """
        encrypted_data = OneLogin_Saml2_XML.to_etree(encrypted_data)
        xmlsec.enable_debug_trace(debug)
        manager = xmlsec.KeysManager()

        manager.add_key(xmlsec.Key.from_memory(key, xmlsec.KeyFormat.PEM, None))
        enc_ctx = xmlsec.EncryptionContext(manager)
        return enc_ctx.decrypt(encrypted_data)

def get_metadata(url):
        """
        Get the metadata XML from the provided URL
        :param url: Url where the XML of the Identity Provider Metadata is published.
        :type url: string
        :returns: metadata XML
        :rtype: string
        """
        valid = False
        response = urllib2.urlopen(url)
        xml = response.read()

        if xml:
            try:
                dom = OneLogin_Saml2_XML.to_etree(xml)
                idp_descriptor_nodes = OneLogin_Saml2_XML.query(dom, '//md:IDPSSODescriptor')
                if idp_descriptor_nodes:
                    valid = True
            except:
                pass

        if not valid:
            raise Exception('Not valid IdP XML found from URL: %s' % (url))

        return xml

:param key: The private key
        :type: string

        :param cert: The public
        :type: string

        :param debug: Activate the xmlsec debug
        :type: bool

        :param sign_algorithm: Signature algorithm method
        :type sign_algorithm: string
        """
        if xml is None or xml == '':
            raise Exception('Empty string supplied as input')

        elem = OneLogin_Saml2_XML.to_etree(xml)
        xmlsec.enable_debug_trace(debug)
        xmlsec.tree.add_ids(elem, ["ID"])
        # Sign the metadata with our private key.
        sign_algorithm_transform_map = {
            OneLogin_Saml2_Constants.DSA_SHA1: xmlsec.Transform.DSA_SHA1,
            OneLogin_Saml2_Constants.RSA_SHA1: xmlsec.Transform.RSA_SHA1,
            OneLogin_Saml2_Constants.RSA_SHA256: xmlsec.Transform.RSA_SHA256,
            OneLogin_Saml2_Constants.RSA_SHA384: xmlsec.Transform.RSA_SHA384,
            OneLogin_Saml2_Constants.RSA_SHA512: xmlsec.Transform.RSA_SHA512
        }
        sign_algorithm_transform = sign_algorithm_transform_map.get(sign_algorithm, xmlsec.Transform.RSA_SHA1)

        signature = xmlsec.template.create(elem, xmlsec.Transform.EXCL_C14N, sign_algorithm_transform, ns='ds')

        issuer = OneLogin_Saml2_XML.query(elem, '//saml:Issuer')
        if len(issuer) > 0:

def get_issuer(request):
        """
        Gets the Issuer of the Logout Request Message
        :param request: Logout Request Message
        :type request: string|DOMDocument
        :return: The Issuer
        :rtype: string
        """

        elem = OneLogin_Saml2_XML.to_etree(request)
        issuer = None
        issuer_nodes = OneLogin_Saml2_XML.query(elem, '/samlp:LogoutRequest/saml:Issuer')
        if len(issuer_nodes) == 1:
            issuer = issuer_nodes[0].text
        return issuer

:type: string

        :param fingerprintalg: The algorithm used to build the fingerprint
        :type: string

        :param validatecert: If true, will verify the signature and if the cert is valid.
        :type: bool

        :param debug: Activate the xmlsec debug
        :type: bool
        """
        try:
            if xml is None or xml == '':
                raise Exception('Empty string supplied as input')

            elem = OneLogin_Saml2_XML.to_etree(xml)
            xmlsec.enable_debug_trace(debug)
            xmlsec.tree.add_ids(elem, ["ID"])

            signature_nodes = OneLogin_Saml2_XML.query(elem, '/samlp:Response/ds:Signature')

            if not len(signature_nodes) > 0:
                signature_nodes += OneLogin_Saml2_XML.query(elem, '/samlp:Response/ds:Signature')
                signature_nodes += OneLogin_Saml2_XML.query(elem, '/samlp:Response/saml:Assertion/ds:Signature')

            if len(signature_nodes) == 1:
                signature_node = signature_nodes[0]

                return OneLogin_Saml2_Utils.validate_node_sign(signature_node, elem, cert, fingerprint, fingerprintalg, validatecert, debug)
            else:
                return False
        except xmlsec.Error as e:

def get_session_indexes(request):
        """
        Gets the SessionIndexes from the Logout Request
        :param request: Logout Request Message
        :type request: string|DOMDocument
        :return: The SessionIndex value
        :rtype: list
        """

        elem = OneLogin_Saml2_XML.to_etree(request)
        session_indexes = []
        session_index_nodes = OneLogin_Saml2_XML.query(elem, '/samlp:LogoutRequest/samlp:SessionIndex')
        for session_index_node in session_index_nodes:
            session_indexes.append(session_index_node.text)
        return session_indexes

:type: string

        :param fingerprintalg: The algorithm used to build the fingerprint
        :type: string

        :param validatecert: If true, will verify the signature and if the cert is valid.
        :type: bool

        :param debug: Activate the xmlsec debug
        :type: bool
        """
        try:
            if xml is None or xml == '':
                raise Exception('Empty string supplied as input')

            elem = OneLogin_Saml2_XML.to_etree(xml)
            xmlsec.enable_debug_trace(debug)
            xmlsec.tree.add_ids(elem, ["ID"])

            signature_nodes = OneLogin_Saml2_XML.query(elem, '/md:EntitiesDescriptor/ds:Signature')

            if len(signature_nodes) == 0:
                signature_nodes += OneLogin_Saml2_XML.query(elem, '/md:EntityDescriptor/ds:Signature')

                if len(signature_nodes) == 0:
                    signature_nodes += OneLogin_Saml2_XML.query(elem, '/md:EntityDescriptor/md:SPSSODescriptor/ds:Signature')
                    signature_nodes += OneLogin_Saml2_XML.query(elem, '/md:EntityDescriptor/md:IDPSSODescriptor/ds:Signature')

            if len(signature_nodes) > 0:
                for signature_node in signature_nodes:
                    if not OneLogin_Saml2_Utils.validate_node_sign(signature_node, elem, cert, fingerprint, fingerprintalg, validatecert, debug):
                        return False