code: @Override
      public void visitTryCatchBlock(Label start, Label end, Label handler, String type) {
          if (type != null) {
              handlers.put(handler, type);
          }
          super.visitTryCatchBlock(start, end, handler, type);
      }
docs: Visit a try catch block. We will use this to determine the exception
  handler labels for the try block.
  
  @param start
  the beginning of the try block
  @param end
  the end of the try block
  @param handler
  the exception handler
  @param type
  the internal name of the throwable being handled