Add map_blocks example to docs. (#3667)
Add map_blocks example to docs. (#3667)


shoyer/xarray,markelg/xray,pydata/xarray,pydata/xarray,shoyer/xarray,jhamman/xarray,pydata/xarray,markelg/xray,markelg/xray,jhamman/xarray,xray/xray,jhamman/xarray