code: protected SortKey getSortKey(String column) {
  
          if (column == null) {
              return null;
          }
          if (column.equals(LIST_COLUMN_ENABLED)) {
              return SortKey.activated;
          } else if (column.equals(LIST_COLUMN_LASTLOGIN)) {
              return SortKey.lastLogin;
          } else if (column.equals(LIST_COLUMN_DISPLAY)) {
              return SortKey.loginName;
          } else if (column.equals(LIST_COLUMN_NAME)) {
              return SortKey.fullName;
          } else if (column.equals(LIST_COLUMN_EMAIL)) {
              return SortKey.email;
          } else if (column.equals(LIST_COLUMN_ORGUNIT)) {
              return SortKey.orgUnit;
          }
          return null;
      }
docs: Returns the sort key for the column.<p>
  
  @param column the list column
  @return the sort key