code: def get_all_instances(self, instance_ids=None, filters=None):
          
          params = {}
          if instance_ids:
              self.build_list_params(params, instance_ids, 'InstanceId')
          if filters:
              if 'group-id' in filters:
                  gid = filters.get('group-id')
                  if not gid.startswith('sg-') or len(gid) != 11:
                      warnings.warn(
                          "The group-id filter now requires a security group "
                          "identifier (sg-*) instead of a group name. To filter "
                          "by group name use the 'group-name' filter instead.",
                          UserWarning)
              self.build_filter_params(params, filters)
          return self.get_list('DescribeInstances', params,
                               [('item', Reservation)], verb='POST')
docs: Retrieve all the instances associated with your account.
  
          :type instance_ids: list
          :param instance_ids: A list of strings of instance IDs
  
          :type filters: dict
          :param filters: Optional filters that can be used to limit
                          the results returned.  Filters are provided
                          in the form of a dictionary consisting of
                          filter names as the key and filter values
                          as the value.  The set of allowable filter
                          names/values is dependent on the request
                          being performed.  Check the EC2 API guide
                          for details.
  
          :rtype: list
          :return: A list of  :class:`boto.ec2.instance.Reservation`