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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 find_source_lines(self):
 """Mark all executable source lines in fn as executed 0 times."""

        strs = trace.find_strings(self.filename)
        lines = trace.find_lines_from_code(self.fn.__code__, strs)
        self.firstcodelineno = sys.maxint
        for lineno in lines:
            self.firstcodelineno = min(self.firstcodelineno, lineno)
            self.sourcelines.setdefault(lineno, 0)
        if self.firstcodelineno == sys.maxint:
            self.firstcodelineno = self.firstlineno