code: public void merge(Model target, BioPAXElement source)
  	{
  		merge(target, Collections.singleton(source));
  	}
docs: Merges the <em>source</em> element (and its "downstream" dependents)
  into <em>target</em> model.
  
  @see #merge(Model, Collection)
  
  @param target the BioPAX model to merge into
  @param source object to add or merge