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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 set_default_headers(self):
        '''
        Set default CORS headers
        '''
        mod_opts = self.application.mod_opts

        if mod_opts.get('cors_origin'):
            origin = self.request.headers.get('Origin')

            allowed_origin = _check_cors_origin(origin, mod_opts['cors_origin'])

            if allowed_origin:
                self.set_header("Access-Control-Allow-Origin", allowed_origin)