code: public Map<String, String> completeByProduct(PCM pcm) throws Exception {
  		
  		Map<String, String> pdtNames2Images = new HashMap<>();
  		
  		List<Product> pdts = pcm.getProducts();
  		for (Product product : pdts) {
  			
  			String productName = product.getKeyCell().getContent();
  			
  			// TODO compute entityID
  			try {
  				String entityID = computeEntityWikidataID(productName);
  							
  				String propertyID = "P41"; //"P154" ; //"P18";  
  				String wikidataImage = "";
  				try {
  					wikidataImage = new WikidataImageRetrieval().retrieve(entityID, propertyID);
  				}
  				catch (Exception e) {
  					try {
  					wikidataImage = new WikidataImageRetrieval().retrieve(entityID, "P154");
  					}
  					catch (Exception e1) {					
  					}				
  				}
  				
  				if (!wikidataImage.isEmpty()) {
  					pdtNames2Images.put(productName, wikidataImage);
  				}
  				else {
  					System.err.println("Image unfound for " + productName);
  				}
  			}
  			catch (Exception e) {
  				System.err.println("Image unfound for " + productName + " because unable to found entity");
  			}
  			
  		}
  		return pdtNames2Images;
  	}
docs: returns a map associating product name to image URL as found in Wikidata
  this map is typically used to add a new column (ft + values) and complete a PCM
  @param pcm
  @return
  @throws Exception