def get_bounds(params):
    """Gets the bounds of the parameters

    A list of ``(min, max)`` pairs will be returned. And the None value for the
    unbound parameters will be kept.

    :param params: An iterable for the model parameters.
    :returns: The list of bounds for the parameters.
    :rtype: list
    """

    return [
        (i.lower, i.upper) for i in params
        ]