transparency in palette mode ( "P" ) images

Dear list,
I have PNG image in  palette mode, with 256 color palette. Every color
has different level of transparency.
For example:
  Color Table (RGB with 256 entries)
    0: 0,0,0,0
    1: 238,238,238,154
    2: 253,253,109,154
    3: 0,0,0,2
    4: 0,0,0,4
    5: 0,0,0,8
    6: 0,0,0,6
    7: 237,237,237,154
    8: 0,0,0,14
    9: 35,35,15,153
   10: 1,1,0,138

I am trying just to open and save this image using PIL.
#!/usr/bin/python
import Image

im = Image.open('test.png')
im.save('out.png', transparency=0 )

After running this code, the resulting image is loosing transparency
information for each color and it is set to 255.
 Color Table (RGB with 256 entries)
    0: 0,0,0,0
    1: 238,238,238,255
    2: 253,253,109,255
    3: 0,0,0,255
    4: 0,0,0,255
    5: 0,0,0,255
    6: 0,0,0,255
    7: 237,237,237,255
    8: 0,0,0,255
    9: 35,35,15,255
   10: 1,1,0,255

Is there any way how to save the image with exactly same palette as
original image ?

For anybody wanting to look at this problem, You can download my test
image here:
http://gista.sk/dl/test.png

Thanks,
Ivan
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