Add a shared volume (i.e. with the ``VOLUME`` command). Not actually written until finalized.

        :param path: Path to the shared volume.

def add_volume(self, path):
        """
        Add a shared volume (i.e. with the ``VOLUME`` command). Not actually written until finalized.

        :param path: Path to the shared volume.
        """
        self.check_not_finalized()
        if self.volumes is None:
            self.volumes = [path]
        else:
            self.volumes.append(path)