How in python select top faces?

Hello everyone, i have a question.
How in python, select top faces?

like this:


I FOUND. I found it in add-ons “3D Print Toolbox”.

Then I corrected it, here:

import bpy, math, bmesh
from mathutils import Vector


def bmesh_copy_from_object(obj, transform=True, triangulate=True, apply_modifiers=False):
    assert(obj.type == 'MESH')


    if apply_modifiers and obj.modifiers:
        import bpy
        me = obj.to_mesh(bpy.context.scene, True, 'PREVIEW', calc_tessface=False)
        bm = bmesh.new(); bm.from_mesh(me); bpy.data.meshes.remove(me)
        del bpy
    else:
        me = obj.data
        if obj.mode == 'EDIT': bm_orig = bmesh.from_edit_mesh(me); bm = bm_orig.copy()
        else: bm = bmesh.new(); bm.from_mesh(me)


    if transform: bm.transform(obj.matrix_world)
    if triangulate: bmesh.ops.triangulate(bm, faces=bm.faces)
    return bm


obj = bpy.context.scene.objects.active
bm = bmesh_copy_from_object(obj, transform=True, triangulate=False); bm.normal_update()


fo = [ele.index for ele in bm.faces if Vector((0, 0, -1.0)).angle(ele.normal, 4.0) > (math.pi / 2.0)]


bpy.ops.mesh.select_all(action='DESELECT')
for i in fo:
    obj = bpy.context.edit_object
    bm = bmesh.from_edit_mesh(obj.data).faces[i].select = True
    bmesh.update_edit_mesh(obj.data, True)