code: public static List<SClassDefinition> getClasses(List<INode> ast)
  	{
  		List<SClassDefinition> classes = new LinkedList<>();
  
  		for (INode n : ast)
  		{
  			if (n instanceof SClassDefinition)
  			{
  				classes.add((SClassDefinition) n);
  			}
  		}
  
  		return classes;
  	}
docs: Convenience method for extracting the VDM class definitions from a list of VDM nodes.
  
  @param ast
  A list of VDM nodes.
  @return The class definitions extracted from <code>ast</code>.