code: public List<BioPAXElement> get(String[] label, Pattern p)
  	{
  		if (label == null) return Collections.emptyList();
  
  		List<BioPAXElement> list = new ArrayList<BioPAXElement>(label.length);
  		for (String lab : label)
  		{
  			list.add(variables[p.indexOf(lab)]);
  		}
  		return list;
  	}
docs: Gets elements corresponding to the given labels in the pattern.
  @param label labels of the element in the pattern
  @param p related pattern
  @return elements of the given label
  @throws IllegalArgumentException if one of the labels not in the pattern