code: public void addConnection(String connectionModel, String nodeType, int fromOrdinal, String viaPropertyName, int toOrdinal) {
          NFBuildGraphNode fromNode = nodeCache.getNode(nodeType, fromOrdinal);
          NFPropertySpec propertySpec = getPropertySpec(nodeType, viaPropertyName);
          int connectionModelIndex = modelHolder.getModelIndex(connectionModel);
  
          NFBuildGraphNode toNode = nodeCache.getNode(propertySpec.getToNodeType(), toOrdinal);
          addConnection(fromNode, propertySpec, connectionModelIndex, toNode);
      }
docs: Add a connection to this graph.  The connection will be in the given connection model.  The connection will be from the node identified by the given
  <code>nodeType</code> and <code>fromOrdinal</code>. The connection will be via the specified <code>viaProperty</code> in the {@link NFNodeSpec} for
  the given <code>nodeType</code>. The connection will be to the node identified by the given <code>toOrdinal</code>.  The type of the to node is implied
  by the <code>viaProperty</code>.