Removed unused assertion method
Removed unused assertion method

cpaulik/xray,kjordahl/xray,chunweiyuan/xarray,rabernat/xray,clarkfitzg/xray,kjordahl/xray,shoyer/xarray,jhamman/xarray,pydata/xarray,NicWayand/xray,jhamman/xarray,shoyer/xray,clarkfitzg/xray,shoyer/xarray,hetland/xray,markelg/xray,petercable/xray,jcmgray/xarray,pydata/xarray,jhamman/xray,rabernat/xray,cpaulik/xray,jhamman/xarray,markelg/xray,markelg/xray,drewokane/xray,pydata/xarray,xray/xray,hetland/xray