// Version&Schema-specific filling into the impl
@Override public FindPojo createImpl() {
FindPojo f = new FindPojo();
// Peel out the Frame from the Key
Value val = DKV.get(key);
if( val == null ) throw new IllegalArgumentException("Key not found");
if( !val.isFrame() ) throw new IllegalArgumentException("Not a Frame");
Frame fr = val.get();
// Peel out an optional column; restrict to this column
if( column != null ) {
Vec vec = fr.vec(column);
if( vec==null ) throw new IllegalArgumentException("Column "+column+" not found in frame "+key);