python Gst.Buffer info unable to set value for field

[Kevron Rees]

 buff = Gst.Buffer.new_allocate(None, 20, None)
 success, info = buff.map(Gst.MapFlags.READ)
 info.data = [1,1,1,1,1]

 RuntimeError: unable to set value for field

I must be doing something stupid...
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