code: @Override
      public KamNode createNode(Integer id, FunctionEnum functionType,
              String label) throws InvalidArgument {
  
          // See if the node already exists
          KamNode kamNode = findNode(id);
  
          if (null == kamNode) {
              kamNode = new KamNodeImpl(this, id, functionType, label);
              // add this node into the graph
              addNode(kamNode);
          } else {
              throw new InvalidArgument("node with id " + id
                      + " already exists in the graph.");
          }
  
          return kamNode;
      }
docs: {@inheritDoc}