code: public CmsJspResourceWrapper getParentFolder() {
  
          if (m_parentFolder == null) {
              String parentFolder = getSitePathParentFolder();
              if (parentFolder != null) {
                  m_parentFolder = readResource(getSitePathParentFolder());
              }
          }
          return m_parentFolder;
      }
docs: Returns the parent folder of this resource in the current site.<p>
  
  In case this resource represents the site root folder, <code>null</code> is returned.<p>
  
  @return the parent folder of this resource in the current site
  
  @see #getSitePathParentFolder()
  @see CmsResource#getParentFolder(String)
  @see org.opencms.jsp.util.CmsJspVfsAccessBean#getParentFolder(Object)