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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_ext_param(self, ext_key, param_key, val):
        '''
        Set the provided parameter in a set of extension parameters.
        '''
        if not self.extensions[ext_key]:
            self.extensions[ext_key] = defaultdict(lambda: None)
        self.extensions[ext_key][param_key] = val