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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_default(self, filename):
 """ A generate which looks in common folders for the default configuration file. The paths goes from system defaults to user specific files. :param filename: The name of the file to find :return: The complete path to the found files """

        for path in self.DEFAULT_PATH:
            # Normalize path
            path = os.path.expanduser(os.path.expandvars(path))
            fullname = os.path.realpath(os.path.join(path, filename))

            if os.path.exists(fullname) and os.path.isfile(fullname):
                yield fullname