def METHOD_NAME(self, err, dataVals=None):
    """Fct to be called before the validity check of the error values."""
    err = np.atleast_1d(err)
    if self.complex:
        if len(err) == 2:
            nData = len(dataVals) // 2
            err = pg.cat(np.ones(nData)*err[0],
                         np.abs(err[1] / dataVals[nData:]))
    else:
        if len(err) == 1:
            err = np.ones(nData)*err[0]
    return err