def _level_and_children(elements):
    """Split a list of elements into elements on the current level (i.e.
    that share the same depth as the first element) and segmented children
    (children of each of those elements)"""
    if not elements:
        return [], []
    depth = elements[0][2]
    level = []
    grouped_children = []
    children = []
    for el in elements:
        if el[2] == depth:
            level.append(el)
            if children:
                grouped_children.append(children)
            children = []
        else:
            children.append(el)
    if children:
        grouped_children.append(children)
    return level, grouped_children
