Takes an InstanceGroup; returns a dict that, when its keys are
        properly prefixed, can be used for describing InstanceGroups in
        RunJobFlow or AddInstanceGroups requests.

def _build_instance_group_args(self, instance_group):
        """
        Takes an InstanceGroup; returns a dict that, when its keys are
        properly prefixed, can be used for describing InstanceGroups in
        RunJobFlow or AddInstanceGroups requests.
        """
        params = {
            'InstanceCount' : instance_group.num_instances,
            'InstanceRole' : instance_group.role,
            'InstanceType' : instance_group.type,
            'Name' : instance_group.name,
            'Market' : instance_group.market
        }
        if instance_group.market == 'SPOT':
            params['BidPrice'] = instance_group.bidprice
        return params