def check_num_columns_in_param_list_arrays(param_list):
    """
    Ensure that each array in param_list, that is not None, has the same number
    of columns. Raises a helpful ValueError if otherwise.

    Parameters
    ----------
    param_list : list of ndarrays or None.

    Returns
    -------
    None.
    """
    try:
        num_columns = param_list[0].shape[1]
        assert all([x is None or (x.shape[1] == num_columns)
                    for x in param_list])
    except AssertionError:
        msg = "param_list arrays should have equal number of columns."
        raise ValueError(msg)

    return None
Ensure that each array in param_list, that is not None, has the same number
    of columns. Raises a helpful ValueError if otherwise.

    Parameters
    ----------
    param_list : list of ndarrays or None.

    Returns
    -------
    None.