selected_child_index refers to the index in the list of 'selected' children and generally differs from that used in
get_child_at_index or returned by
selected_child_index must lie
between 0 and get_n_selected_children - 1, inclusive.
a pointer to the Selection on which to operate.
a int indicating which of the selected children is specified.
a pointer to a selected Accessible child object, specified by