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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 add_coverage(self, qname, sname, qcover, scover=None):
 """Add percentage coverage values to self.alignment_coverage."""

        self.alignment_coverage.loc[qname, sname] = qcover
        if scover:
            self.alignment_coverage.loc[sname, qname] = scover