How to access custom node label in html file

Hi,
I have seen the following code in core inject node (20-inject.html)

var label = this._def.label.call(this);

I would like to do the same in my custom node to access the node label. But... I am getting "_def of undefined" error.

Tried another way that is in the same core inject node (20-inject.html).

var label = this._(name);
getting "_ of undefined" error

Can any please suggest what is wrong and how to fix it.

Thanks in advance

Is this in your oneditprepare function? If so, how exactly have you defined the function?