tv_stack_frame_stack

t3toolbox.backend.tv_operations.tv_stack_frame_stack(paired_tree)

def tv_stack_frame_stack(
        paired_tree,  # array-like tree (shape G) of (frame_data, variations_data) pairs
):  # -> (
    #        frame-data,       # stack = G
    #        variations-data,  # stack = K + C
    #    )

Stack a C-shaped tree of (frame_data, variations_data) pairs over the frame stack C.

The frame stack is placed innermost (the variation stack becomes K + C), matching the frame-inner convention. Takes exactly the paired-tree layout that tv_unstack_frame_stack() produces (its inverse), so a backend user round-trips without splitting the pairs by hand.