code: def _select_source_arch(self, source, source64):
          
          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
docs: Return sources by arch