Dumps string as UTF8 encoded string
    :param writer:
    :param elem:
    :return:

async def dump_unicode(writer, elem):
    """
    Dumps string as UTF8 encoded string
    :param writer:
    :param elem:
    :return:
    """
    await dump_uvarint(writer, len(elem))
    await writer.awrite(bytes(elem, 'utf8'))