code: @Override
      public void visitClassContext(final ClassContext classContext) {
          try {
              stack = new OpcodeStack();
              memberCollections = new HashMap<>();
              memberSourceLineAnnotations = new HashMap<>();
              super.visitClassContext(classContext);
          } finally {
              stack = null;
              memberCollections = null;
              memberSourceLineAnnotations = null;
          }
      }
docs: implements the visitor to create and destroy the stack and member collections
  
  @param classContext
  the context object for the currently parsed class