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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 initial_update(self, mapping):
        '''Initially fills the underlying dictionary with keys, values and
        timestamps.
        '''
        for key, val in mapping.items():
            _, timestamp = val
            if not self.TTL or (datetime.utcnow() -
                datetime.utcfromtimestamp(timestamp) < self.TTL):
                self.__setitem__(key, val, raw=True)