Save this package to *pkg_file*, where *file* can be either a path to
        a file (a string) or a file-like object.

def save(self, pkg_file):
        """
        Save this package to *pkg_file*, where *file* can be either a path to
        a file (a string) or a file-like object.
        """
        for part in self.parts:
            part.before_marshal()
        PackageWriter.write(pkg_file, self.rels, self.parts)