What is opt used for in some nodes' validate:function(v,opt)

Developing Nodes
1

Node properties : Node-RED describes how the validate function can be used.
Its signature is given as validate:function(v)

But then I saw in the delay node

 validate:function(v,opt) {
      if (RED.validators.number(v) && (v >= 0)) {
          return true;
      }
      return RED._("node-red:delay.errors.invalid-timeout");
  }},

What is the second parameter (opt) used for?

2

Hi,
Its a message that will be displayed if you place your cursor on the red triangle at the top right of your node. See here.