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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 _symbol_trades(self, symbols):
        '''
        Query last_trade in parallel for multiple symbols and
        return in dict.

        symbols: list[str]

        return: dict[str -> polygon.Trade]
        '''

        @skip_http_error((404, 504))
        def fetch(symbol):
            return self._api.polygon.last_trade(symbol)

        return parallelize(fetch)(symbols)