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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_instances(self, state_filter=None):
 """ Get all the instances filtered by state. @param state_filter: the state that the instance should be in (e.g. "running"), or None for all states """


    instances = []
    for instance in self._get_instances(self._get_cluster_group_name(), 
                                        state_filter):
      instances.append(Instance(instance.id, instance.dns_name, 
                                instance.private_dns_name, 
                                instance.private_ip_address))
    return instances