Callback function to spawn a mini-browser when a feature is clicked.

def callback(self, event):
        """
        Callback function to spawn a mini-browser when a feature is clicked.
        """
        artist = event.artist
        ind = artist.ind
        limit = 5
        browser = True
        if len(event.ind) > limit:
            print "more than %s genes selected; not spawning browsers" % limit
            browser = False
        for i in event.ind:
            feature = artist.features[ind[i]]
            print feature,
            if browser:
                self.minibrowser.plot(feature)