How to use the onelogin.saml2.utils.OneLogin_Saml2_Utils.decrypt_element function in onelogin

if 'RetrievalMethod' in child.tag:
                        if child.attrib['Type'] != 'http://www.w3.org/2001/04/xmlenc#EncryptedKey':
                            raise OneLogin_Saml2_ValidationError(
                                'Unsupported Retrieval Method found',
                                OneLogin_Saml2_ValidationError.UNSUPPORTED_RETRIEVAL_METHOD
                            )
                        uri = child.attrib['URI']
                        if not uri.startswith('#'):
                            break
                        uri = uri.split('#')[1]
                        encrypted_key = OneLogin_Saml2_Utils.query(encrypted_assertion_nodes[0], './xenc:EncryptedKey[@Id=$tagid]', None, uri)
                        if encrypted_key:
                            keyinfo.append(encrypted_key[0])

                encrypted_data = encrypted_data_nodes[0]
                decrypted = OneLogin_Saml2_Utils.decrypt_element(encrypted_data, key, debug=debug, inplace=True)
                dom.replace(encrypted_assertion_nodes[0], decrypted)

        return dom

if not children:
                    raise Exception('No child to KeyInfo, invalid Assertion')
                for child in children:
                    if 'RetrievalMethod' in child.tag:
                        if child.attrib['Type'] != 'http://www.w3.org/2001/04/xmlenc#EncryptedKey':
                            raise Exception('Unsupported Retrieval Method found')
                        uri = child.attrib['URI']
                        if not uri.startswith('#'):
                            break
                        uri = uri.split('#')[1]
                        encrypted_key = OneLogin_Saml2_XML.query(encrypted_assertion_nodes[0], './xenc:EncryptedKey[@Id="' + uri + '"]')
                        if encrypted_key:
                            keyinfo.append(encrypted_key[0])

                encrypted_data = encrypted_data_nodes[0]
                decrypted = OneLogin_Saml2_Utils.decrypt_element(encrypted_data, key, debug)
                xml.replace(encrypted_assertion_nodes[0], decrypted)
        return xml

def get_nameid_data(self):
        """
        Gets the NameID Data provided by the SAML Response from the IdP

        :returns: Name ID Data (Value, Format, NameQualifier, SPNameQualifier)
        :rtype: dict
        """
        nameid = None
        nameid_data = {}

        encrypted_id_data_nodes = self.__query_assertion('/saml:Subject/saml:EncryptedID/xenc:EncryptedData')
        if encrypted_id_data_nodes:
            encrypted_data = encrypted_id_data_nodes[0]
            key = self.__settings.get_sp_key()
            nameid = OneLogin_Saml2_Utils.decrypt_element(encrypted_data, key)
        else:
            nameid_nodes = self.__query_assertion('/saml:Subject/saml:NameID')
            if nameid_nodes:
                nameid = nameid_nodes[0]

        is_strict = self.__settings.is_strict()
        want_nameid = self.__settings.get_security_data().get('wantNameId', True)
        if nameid is None:
            if is_strict and want_nameid:
                raise OneLogin_Saml2_ValidationError(
                    'NameID not found in the assertion of the Response',
                    OneLogin_Saml2_ValidationError.NO_NAMEID
                )
        else:
            if is_strict and want_nameid and not OneLogin_Saml2_Utils.element_text(nameid):
                raise OneLogin_Saml2_ValidationError(

elem = fromstring(request, forbid_dtd=True)

        name_id = None
        encrypted_entries = OneLogin_Saml2_Utils.query(elem, '/samlp:LogoutRequest/saml:EncryptedID')

        if len(encrypted_entries) == 1:
            if key is None:
                raise OneLogin_Saml2_Error(
                    'Private Key is required in order to decrypt the NameID, check settings',
                    OneLogin_Saml2_Error.PRIVATE_KEY_NOT_FOUND
                )

            encrypted_data_nodes = OneLogin_Saml2_Utils.query(elem, '/samlp:LogoutRequest/saml:EncryptedID/xenc:EncryptedData')
            if len(encrypted_data_nodes) == 1:
                encrypted_data = encrypted_data_nodes[0]
                name_id = OneLogin_Saml2_Utils.decrypt_element(encrypted_data, key)
        else:
            entries = OneLogin_Saml2_Utils.query(elem, '/samlp:LogoutRequest/saml:NameID')
            if len(entries) == 1:
                name_id = entries[0]

        if name_id is None:
            raise OneLogin_Saml2_ValidationError(
                'NameID not found in the Logout Request',
                OneLogin_Saml2_ValidationError.NO_NAMEID
            )

        name_id_data = {
            'Value': OneLogin_Saml2_Utils.element_text(name_id)
        }
        for attr in ['Format', 'SPNameQualifier', 'NameQualifier']:
            if attr in name_id.attrib.keys():

:type key: string
        :return: Name ID Data (Value, Format, NameQualifier, SPNameQualifier)
        :rtype: dict
        """
        elem = OneLogin_Saml2_XML.to_etree(request)
        name_id = None
        encrypted_entries = OneLogin_Saml2_XML.query(elem, '/samlp:LogoutRequest/saml:EncryptedID')

        if len(encrypted_entries) == 1:
            if key is None:
                raise Exception('Key is required in order to decrypt the NameID')

            encrypted_data_nodes = OneLogin_Saml2_XML.query(elem, '/samlp:LogoutRequest/saml:EncryptedID/xenc:EncryptedData')
            if len(encrypted_data_nodes) == 1:
                encrypted_data = encrypted_data_nodes[0]
                name_id = OneLogin_Saml2_Utils.decrypt_element(encrypted_data, key)
        else:
            entries = OneLogin_Saml2_XML.query(elem, '/samlp:LogoutRequest/saml:NameID')
            if len(entries) == 1:
                name_id = entries[0]

        if name_id is None:
            raise Exception('Not NameID found in the Logout Request')

        name_id_data = {
            'Value': name_id.text
        }
        for attr in ['Format', 'SPNameQualifier', 'NameQualifier']:
            if attr in name_id.attrib:
                name_id_data[attr] = name_id.attrib[attr]

        return name_id_data