def unique_size(self):
        """
        Size of ONLY this particular layer

        :return: int or None
        """
        self._virtual_size = self._virtual_size or \
                             graceful_chain_get(self.data, "VirtualSize", default=0)
        try:
            return self._virtual_size - self._shared_size
        except TypeError:
            return 0
Size of ONLY this particular layer

        :return: int or None