Creates a CustomJS callback that will send the requested
        attributes back to python.

def get_customjs(self, references, plot_id=None):
        """
        Creates a CustomJS callback that will send the requested
        attributes back to python.
        """
        # Generate callback JS code to get all the requested data
        if plot_id is None:
            plot_id = self.plot.id or 'PLACEHOLDER_PLOT_ID'
        self_callback = self.js_callback.format(comm_id=self.comm.id,
                                                timeout=self.timeout,
                                                debounce=self.debounce,
                                                plot_id=plot_id)

        attributes = self.attributes_js(self.attributes)
        conditions = ["%s" % cond for cond in self.skip]
        conditional = ''
        if conditions:
            conditional = 'if (%s) { return };\n' % (' || '.join(conditions))
        data = "var data = {};\n"
        code = conditional + data + attributes + self.code + self_callback
        return CustomJS(args=references, code=code)