code: public I_CmsXmlContentValue addValue(CmsObject cms, String xpath, int index) {
  
          I_CmsXmlContentValue newValue = m_content.addValue(cms, xpath, getLocale(), index);
  
          // re-initialize the value list
          m_values = m_content.getValues(getPath(), getLocale());
  
          return newValue;
      }
docs: Adds a value element of the type indicated by the given xpath
  at the selected index to the XML content document.<p>
  
  @param cms the current users OpenCms context
  @param xpath the path that indicates the element type in the content definition
  @param index the index where to add the new value element
  
  @return the added XML content value element
  
  @see CmsXmlContent#addValue(CmsObject, String, Locale, int)
  @see #addValue(CmsObject, I_CmsXmlSchemaType, int)
  @see #addValue(CmsObject, int)