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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 size(self):
 """ Return directory size in bytes. :rtype: int :return: Total directory size in bytes. """

        dir_size = 0
        for f in self.iterfiles(abspath=True):
            dir_size += os.path.getsize(f)
        return dir_size