Column listeners in Extjs

Question

I am trying to figure out what my arguments are on a click event on a grid column in Extjs 4.

xtype: 'gridpanel',
columns: [{
    header: 'col1',
    dataIndex: 'col1',
    flex: 0.5,
    listeners: {
        click: function () {
            alert('what are my arguments? ' + arguments)
        }
    }
}, {
    header: 'col12',
    dataIndex: 'col2',
    flex: 0.5
}]

I know that the arguments look something like this :

However this is not really helpful due to the 'ducktyping' nature of Javascript. Specifically I want the record, however I can't be 100% sure if I just choose an object that looks like the right thing.

More fundamentally, I am not exactly sure how the API documentation works in Extjs4. If I want to see what arguments are being passed in the click event I would expect to be able to go to the column object (Ext.grid.column.Column), and look at its click event. However if I look I cannot find any click event.

Am I understanding something wrong?