def render_css_classes(self):
        """
        Return a string containing the css classes for the module.

        >>> mod = DashboardModule(enabled=False, draggable=True,
        ...                       collapsible=True, deletable=True)
        >>> mod.render_css_classes()
        'dashboard-module disabled draggable collapsible deletable'
        >>> mod.css_classes.append('foo')
        >>> mod.render_css_classes()
        'dashboard-module disabled draggable collapsible deletable foo'
        >>> mod.enabled = True
        >>> mod.render_css_classes()
        'dashboard-module draggable collapsible deletable foo'
        """
        ret = ['dashboard-module']
        if not self.enabled:
            ret.append('disabled')
        if self.draggable:
            ret.append('draggable')
        if self.collapsible:
            ret.append('collapsible')
        if self.deletable:
            ret.append('deletable')
        ret += self.css_classes
        return ' '.join(ret)
Return a string containing the css classes for the module.

        >>> mod = DashboardModule(enabled=False, draggable=True,
        ...                       collapsible=True, deletable=True)
        >>> mod.render_css_classes()
        'dashboard-module disabled draggable collapsible deletable'
        >>> mod.css_classes.append('foo')
        >>> mod.render_css_classes()
        'dashboard-module disabled draggable collapsible deletable foo'
        >>> mod.enabled = True
        >>> mod.render_css_classes()
        'dashboard-module draggable collapsible deletable foo'