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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 start_instances(self, instance_ids=None):
 """ Start the instances specified :type instance_ids: list :param instance_ids: A list of strings of the Instance IDs to start :rtype: list :return: A list of the instances started """

        params = {}
        if instance_ids:
            self.build_list_params(params, instance_ids, 'InstanceId')
        return self.get_list('StartInstances', params,
                             [('item', Instance)], verb='POST')