def child(idx, dim, axis):
    """
    Child node according to Bertran's notation.

    Parameters
    ----------
    idx : int
        Index of the parent node.
    dim : int
        Dimensionality of the problem.
    axis : int
        Dimension direction to define a child.
        Must have `0<=axis<dim`

    Returns
    -------
    out : int
        Index of child node with `out > idx`.

    Examples
    --------
    >>> print(chaospy.bertran.child(4, 1, 0))
    5
    >>> print(chaospy.bertran.child(4, 2, 1))
    8
    """
    idxm = multi_index(idx, dim)
    out = numpy.array(idxm) + 1*(numpy.eye(len(idxm))[axis])
    return single_index(out)
Child node according to Bertran's notation.

    Parameters
    ----------
    idx : int
        Index of the parent node.
    dim : int
        Dimensionality of the problem.
    axis : int
        Dimension direction to define a child.
        Must have `0<=axis<dim`

    Returns
    -------
    out : int
        Index of child node with `out > idx`.

    Examples
    --------
    >>> print(chaospy.bertran.child(4, 1, 0))
    5
    >>> print(chaospy.bertran.child(4, 2, 1))
    8