def flatten_list(array):
    """Flattens an array by removing 1 level of nesting.

    Parameters
    ----------
    array : `list` [`list`]
        List of lists.

    Returns
    -------
    flat_arr : `list`
        Removes one level of nesting from the array.
        [[4], [3, 2], [1, [0]]] becomes [4, 3, 2, 1, [0]].
    """
    return [item for sublist in array for item in sublist]