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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_all_current_trains(self, train_type=None, direction=None):
 """Returns all trains that are due to start in the next 10 minutes @param train_type: ['mainline', 'suburban', 'dart'] """

        params = None
        if train_type:
            url = self.api_base_url + 'getCurrentTrainsXML_WithTrainType'
            params = {
                'TrainType': STATION_TYPE_TO_CODE_DICT[train_type]
            }
        else:
            url = self.api_base_url + 'getCurrentTrainsXML'

        response = requests.get(
            url, params=params, timeout=10)

        if response.status_code != 200:
            return []

        trains = self._parse_all_train_data(response.content)

        if direction is not None:
            return self._prune_trains(trains, direction=direction)

        return trains