def _validate_l1_method(method):
    """
    As of 0.10.0, the supported values for `method` in `fit_regularized`
    are "l1" and "l1_cvxopt_cp".  If an invalid value is passed, raise
    with a helpful error message

    Parameters
    ----------
    method : str

    Raises
    ------
    ValueError
    """
    if method not in ['l1', 'l1_cvxopt_cp']:
        raise ValueError(
            '`method` = {method} is not supported, use either "l1" or "l1_cvxopt_cp"'
            .format(method=method))
