def get_valid_paths(self, path):
        """
        There are some restrictions on the valid directory structures:

        1. There can be only one vasp run in each directory. Nested directories
           are fine.
        2. Directories designated "relax1", "relax2" are considered to be 2
           parts of an aflow style run.
        3. Directories containing vasp output with ".relax1" and ".relax2" are
           also considered as 2 parts of an aflow style run.
        """
        (parent, subdirs, files) = path
        if set(self.runs).intersection(subdirs):
            return [parent]
        if not any([parent.endswith(os.sep + r) for r in self.runs]) and \
                len(glob.glob(os.path.join(parent, "vasprun.xml*"))) > 0:
            return [parent]
        return []