code: private Map<String, AttributeValue> convertToItem(Map<String, AttributeValueUpdate> putValues) {
          Map<String, AttributeValue> map = new HashMap<String, AttributeValue>();
          for ( Entry<String, AttributeValueUpdate> entry : putValues.entrySet() ) {
              /*
               * AttributeValueUpdate allows nulls for its values, since they are
               * semantically meaningful. AttributeValues never have null values.
               */
              if ( entry.getValue().getValue() != null )
                  map.put(entry.getKey(), entry.getValue().getValue());
          }
          return map;
      }
docs: Converts the {@link AttributeValueUpdate} map given to an equivalent
  {@link AttributeValue} map.