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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 error_uns(self):
 """Check if package supported by arch before proceed to install """

        self.FAULT = ""
        UNST = ["UNSUPPORTED", "UNTESTED"]
        if "".join(self.source_dwn) in UNST:
            self.FAULT = "".join(self.source_dwn)