def odd(n, add=1):
    """Return next odd integer to `n`.

    Can be used to construt odd smoothing kernels in :func:`smooth`.

    Parameters
    ----------
    n : int
    add : int
        number to add if `n` is even, +1 or -1
    """
    assert add in [-1, 1], "add must be -1 or 1"
    return n if n % 2 == 1 else n + add