override equals in IndexVariable
override equals in IndexVariable

shoyer/xarray,shoyer/xray,rabernat/xray,jhamman/xray,pydata/xarray,chunweiyuan/xarray,jhamman/xarray,shoyer/xarray,rabernat/xray,markelg/xray,jhamman/xarray,markelg/xray,pydata/xarray,xray/xray,jhamman/xarray,jcmgray/xarray,pydata/xarray,markelg/xray