code: private static Set<String> populateContributors(Set<String> source, Set<String> destination) {
  		for (String contributor : source) {
  			if (!emailPattern.matcher(contributor).matches()) {
  				LOGGER.warning("The contributor '" + contributor + "' does not respect the email pattern " + emailPattern.pattern() + " and is ignored");
  			}
  			else if (destination.contains(contributor)) {
  				LOGGER.info("The contributor '" + contributor + "' is already present in the collection and is ignored");
  			}
  			else {
  				destination.add(contributor);
  			}
  		}
  		return destination;
  	}
docs: Populate the source with the destination contributors only if they match the pattern rules for the contributors
  
  @param source The source to check
  @param destination The destination to fill
  @return The destination updated