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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 _file_list(self, folder):
        '''returns a list of file names in an sosreport directory'''
        rtn = []
        walk = self._walk_report(folder)
        for key,val in walk.items():
            for v in val:
                x=os.path.join(key,v)
                rtn.append(x)

        self.file_count = len(rtn)  #a count of the files we'll have in the final cleaned sosreport, for reporting
        return rtn