code: public static Collection<RoboconfError> findWarnings( Collection<? extends RoboconfError> errors ) {
  
  		Collection<RoboconfError> result = new ArrayList<> ();
  		for( RoboconfError error : errors ) {
  			if( error.getErrorCode().getLevel() == ErrorLevel.WARNING )
  				result.add( error );
  		}
  
  		return result;
  	}
docs: Finds all the warnings among a collection of Roboconf errors.
  @param errors a non-null collection of errors
  @return a non-null collection of warnings