Root level init
        :return:

async def root(self):
        """
        Root level init
        :return:
        """
        if self.writing:
            await x.dump_uint(self.iobj, PortableStorageConsts.SIGNATUREA, 4)
            await x.dump_uint(self.iobj, PortableStorageConsts.SIGNATUREB, 4)
            await x.dump_uint(self.iobj, PortableStorageConsts.FORMAT_VER, 1)

        else:
            sig_a = await x.load_uint(self.iobj, 4)
            sig_b = await x.load_uint(self.iobj, 4)
            ver = await x.load_uint(self.iobj, 1)

            if sig_a != PortableStorageConsts.SIGNATUREA:
                raise ValueError('Signature A error')
            if sig_b != PortableStorageConsts.SIGNATUREB:
                raise ValueError('Signature A error')
            if ver != PortableStorageConsts.FORMAT_VER:
                raise ValueError('Unsupported version')