public void add(Node component) {
        if (nodesById.containsKey(component.componentId())) {
            throw new IllegalStateException("Multiple components with the same id " + component.componentId());
        }
        nodesById.put(component.componentId(), component);
    }
@author Tony Vaagenes
@author gjoranv
@author ollivir

Not thread safe.
container-core/src/main/java/com/yahoo/container/di/componentgraph/core/ComponentGraph.java