@classmethod
def get_software_package_version(cls, calc, **kwargs):
    """
        Returns software package version used to compute and produce
        the computed structure file. Only version designator should be
        used, e.g. '3.4.0', '2.1rc3'.
        """
    try:
        return calc.out.job_info.get_dict()['nwchem branch']
    except Exception:
        return None
