code: protected List<INode> getUserModules(List<? extends INode> ast)
  	{
  		List<INode> userModules = new LinkedList<INode>();
  
  		for (INode node : ast)
  		{
  			if (!getInfo().getDeclAssistant().isLibrary(node))
  			{
  				userModules.add(node);
  			}
  		}
  
  		return userModules;
  	}
docs: This method extracts the user modules or classes from a VDM AST.
  
  @param ast
  The VDM AST.
  @return A list of user modules or classes.