def to_one_index_slice(s):
    """Convert 0-based to 1-based position.

    Parameters
    ----------
    s : slice

    Returns
    -------
    slice

    Example
    -------
    Assumes that values are both positive or both negative.
    Coordinate values are positive:
    >>> s1 = slice(0, 5)
    >>> to_one_index_slice(s1)
    slice(1, 5, None)
    >>> s2 = slice(10, 50)
    >>> to_one_index_slice(s2)
    slice(11, 50, None)

    Coordinate values are negative:
    >>> s3 = slice(-1, -5)
    >>> to_one_index_slice(s3)
    slice(-1, -4, None)
    >>> s4 = slice(-5, -10)
    >>> to_one_index_slice(s4)
    slice(-5, -9, None)

    """
    if s.start < 0:
        return slice(s.start, s.stop + 1, s.step)
    return slice(s.start + 1, s.stop, s.step)
