Recursively create grid from input lists.

def _create_grid(iterable, sizing_mode, layer=0):
    """Recursively create grid from input lists."""
    return_list = []
    for item in iterable:
        if isinstance(item, list):
            return_list.append(_create_grid(item, sizing_mode, layer+1))
        elif isinstance(item, LayoutDOM):
            if sizing_mode is not None and _has_auto_sizing(item):
                item.sizing_mode = sizing_mode
            return_list.append(item)
        else:
            raise ValueError(
                """Only LayoutDOM items can be inserted into a layout.
                Tried to insert: %s of type %s""" % (item, type(item))
            )
    if layer % 2 == 0:
        return column(children=return_list, sizing_mode=sizing_mode)
    return row(children=return_list, sizing_mode=sizing_mode)