code: def render_css_classes(self):
          
          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)
docs: 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'