public Optional<DeploymentInstanceSpec> instance(InstanceName name) {
        for (DeploymentInstanceSpec instance : instances()) {
            if (instance.name().equals(name))
                return Optional.of(instance);
        }
        return Optional.empty();
    }
Returns the instance step containing the given instance name
config-model-api/src/main/java/com/yahoo/config/application/api/DeploymentSpec.java