How to use the xmlsec.Key.from_memory function in xmlsec

def test_encrypt_xml():
    # Load the public cert
    manager = xmlsec.KeysManager()
    filename = path.join(BASE_DIR, 'rsacert.pem')
    key = xmlsec.Key.from_memory(read_from_file(filename), xmlsec.KeyFormat.CERT_PEM, None)
    assert key is not None
    manager.add_key(key)
    template = parse_xml('enc1-doc.xml')
    assert template is not None
    # Prepare for encryption
    enc_data = xmlsec.template.encrypted_data_create(
        template, xmlsec.Transform.AES128, type=xmlsec.EncryptionType.ELEMENT, ns="xenc")

    xmlsec.template.encrypted_data_ensure_cipher_value(enc_data)
    key_info = xmlsec.template.encrypted_data_ensure_key_info(enc_data, ns="dsig")
    enc_key = xmlsec.template.add_encrypted_key(key_info, xmlsec.Transform.RSA_OAEP)
    xmlsec.template.encrypted_data_ensure_cipher_value(enc_key)

    data = template.find('./Data')

    assert data is not None

:param key: The private key
        :type: string

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

        :return signed message
        :rtype str
        """

        if isinstance(msg, str):
            msg = msg.encode('utf8')

        xmlsec.enable_debug_trace(debug)
        dsig_ctx = xmlsec.SignatureContext()
        dsig_ctx.key = xmlsec.Key.from_memory(key, xmlsec.KeyFormat.PEM, None)
        return dsig_ctx.sign_binary(compat.to_bytes(msg), algorithm)

def _make_verify_key(cert_data):
    key = xmlsec.Key.from_memory(cert_data, xmlsec.KeyFormat.CERT_PEM, None)
    return key

def load_key_from_data(key_data, cert_data=None, password=None, key_format="PEM"):
    key_format = get_key_format_value(key_format)
    key = xmlsec.Key.from_memory(key_data, key_format, password)
    if cert_data:
        key.load_cert_from_memory(cert_data, key_format)
    return key

: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)

issuer.addnext(signature)
        else:
            elem[0].insert(0, signature)

        elem_id = elem.get('ID', None)
        if elem_id:
            elem_id = '#' + elem_id

        ref = xmlsec.template.add_reference(signature, xmlsec.Transform.SHA1, uri=elem_id)
        xmlsec.template.add_transform(ref, xmlsec.Transform.ENVELOPED)
        xmlsec.template.add_transform(ref, xmlsec.Transform.EXCL_C14N)
        key_info = xmlsec.template.ensure_key_info(signature)
        xmlsec.template.add_x509_data(key_info)

        dsig_ctx = xmlsec.SignatureContext()
        sign_key = xmlsec.Key.from_memory(key, xmlsec.KeyFormat.PEM, None)
        sign_key.load_cert_from_memory(cert, xmlsec.KeyFormat.PEM)

        dsig_ctx.key = sign_key
        dsig_ctx.sign(signature)

        return OneLogin_Saml2_XML.to_string(elem)

def _make_sign_key(key_data, cert_data, password):
    key = xmlsec.Key.from_memory(key_data, xmlsec.KeyFormat.PEM, password)
    key.load_cert_from_memory(cert_data, xmlsec.KeyFormat.PEM)
    return key