[mono-cecil] Binary file output is different each time AssemblyFactory.SaveAssembly is called

[JohnC]

Even if the input file (to AssemblyFactory.ReadAssembly) is the same,
every call to AssemblyFactory.SaveAssembly  creates a file which is
binary different from pervious ones.

What causes this? Is this a bug ? Can this behavior be changed?

Thanks,

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mono-cecil