code: public void removeAttributeValue(String attributeName, int index) {
  
          if (m_simpleAttributes.containsKey(attributeName)) {
              List<String> values = m_simpleAttributes.get(attributeName);
              if ((values.size() == 1) && (index == 0)) {
                  removeAttributeSilent(attributeName);
              } else {
                  values.remove(index);
              }
          } else if (m_entityAttributes.containsKey(attributeName)) {
              List<CmsEntity> values = m_entityAttributes.get(attributeName);
              if ((values.size() == 1) && (index == 0)) {
                  removeAttributeSilent(attributeName);
              } else {
                  CmsEntity child = values.remove(index);
                  removeChildChangeHandler(child);
              }
          }
          fireChange();
      }
docs: Removes a specific attribute value.<p>
  
  @param attributeName the attribute name
  @param index the value index