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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _select_source_arch(self, source, source64):
 """Return sources by arch """

        src = ""
        if self.meta.arch == "x86_64":
            if source64:
                src = source64
            else:
                src = source
            if self.meta.skip_unst in self.answer and source64 in self.unst:
                src = source
        else:
            if source:
                src = source
            if self.meta.skip_unst in self.answer and source in self.unst:
                src = source64
        return src