final ImmutableMap.Builder<KijiColumnName, KijiCellDecoder<?>> decoderMap =
ImmutableMap.builder();
for (KijiColumnName column : columns) {
// Gets the specification for this column,
// from the overlay map or else from the actual table layout:
final BoundColumnReaderSpec spec = overrides.get(column);
if (null != spec) {
decoderMap.put(column, createDecoderFromSpec(layout, spec));
} else {
final CellSpec cellSpec = layout.getCellSpec(column);
decoderMap.put(column, cellSpec.getDecoderFactory().create(cellSpec));