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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 get_file_view_cls(self, filename):
 """Returns the view class associated to a filename """

        if filename is None:
            return self.default_view_class
        for pattern, cls in self.view_class_files_map:
            if pattern.match(filename):
                return cls
        return self.default_view_class