def bound_elems(elems):
group_x0 = min(map(lambda l: l.x0, elems))<EOL>group_y0 = min(map(lambda l: l.y0, elems))<EOL>group_x1 = max(map(lambda l: l.x1, elems))<EOL>group_y1 = max(map(lambda l: l.y1, elems))<EOL>return (group_x0, group_y0, group_x1, group_y1)<EOL>
Finds the minimal bbox that contains all given elems