code: public WidgetBuilder selectorAttr(String name, String value) throws IOException {
          if (value != null) {
              ResponseWriter rw = context.getResponseWriter();
              rw.write(",");
              rw.write(name);
              rw.write(":\"");
              rw.write(ComponentUtils.escapeSelector(value));
              rw.write("\"");
          }
  
          return this;
      }
docs: This should only be used internally if the selector is directly used by jQuery on the client.
  If PFS is used and specified by the user, {@link #attr(java.lang.String, java.lang.String)} should be used
  as the users have to escape colons like @(myForm\:myId).
  
  @param name
  @param value
  @return
  @throws IOException