compute and set our version

def set_version(self):
        """ compute and set our version """
        version = _ensure_decoded(
            getattr(self.group._v_attrs, 'pandas_version', None))
        try:
            self.version = tuple(int(x) for x in version.split('.'))
            if len(self.version) == 2:
                self.version = self.version + (0,)
        except AttributeError:
            self.version = (0, 0, 0)