Slice a numpy array to make columns

    Parameters
    ----------
    x : ndarray
        A numpy array instance
    using : list of integer or slice instance or None, optional
        A list of index or slice instance

    Returns
    -------
    ndarray
        A list of numpy array columns sliced

def slice_columns(x, using=None):
    """
    Slice a numpy array to make columns

    Parameters
    ----------
    x : ndarray
        A numpy array instance
    using : list of integer or slice instance or None, optional
        A list of index or slice instance

    Returns
    -------
    ndarray
        A list of numpy array columns sliced

    """
    if using is None:
        using = range(0, len(x[0]))
    return [x[:,s] for s in using]