How do I change the autoindent to 2 space in IPython notebook

I find that developing functions in IPython notebook allows me to work quickly. When I'm happy with the results I copy-paste to a file. The autoindent is 4 spaces, but the coding style for indentation at my company is 2 spaces. How do I change the autoindent to 2 spaces?

Based on this question and the options found here:
In your custom.js file (location depends on your OS) put

IPython.Cell.options_default.cm_config.indentUnit = 2;

On my machine the file is located in ~/.ipython/profile_default/static/custom

Update:

In IPython 3 the plain call does not work any more, thus it is required to place the setting within an appropriate event handler. A possible solution could look like

define([
    'base/js/namespace',
    'base/js/events'
    ],
    function(IPython, events) {
        events.on("app_initialized.NotebookApp",
            function () {
                IPython.Cell.options_default.cm_config.indentUnit = 2;
            }
        );
    }
);