This is not really doing much, and it is a bit misleading. I propose taking it out. 

The reason why its a bit misleading is because the withContext method on RasterRDD actually mutates the RasterRDD - it adds the context to the rdd. So its better to keep the calling of it explicit at the end of making all rdd operations.

e.g.,  self.mapPartitions({ partition =>
        partition.map { tile =>
          f(tile, d)
        }
      }, true).withContext(opCtx)