class MyMenuProvider(QgsLayerTreeViewMenuProvider):
def __init__(self, view):
    QgsLayerTreeViewMenuProvider.__init__(self)
    self.view = view

  def createContextMenu(self):
    if not self.view.currentLayer():
      return None
    m = QMenu()
    m.addAction("Show Attribute Table", self.openAttributeTable)
    return m

  def openAttributeTable(self):
    #iface1.openFeatureForm(iface1.activeLayer(), feature, False)
    iface1.showAttributeTable(iface1.activeLayer())

view = iface1.layerTreeView()
 provider = MyMenuProvider(view)
 view.setMenuProvider(provider)