public String throwableToString(){
  StringBuilder sb=new StringBuilder("Exception:  ");
  if (throwable != null)   sb.append(throwable.toString());
 else   sb.append("null");
  sb.append("\n");
  return sb.toString();
}

public String throwableToString ( ) { StringBuilder sb = new StringBuilder ( "Exception:  " ) ; if ( throwable != null ) sb . append ( throwable . toString ( ) ) ; else sb . append ( "null" ) ; sb . append ( "\n" ) ; return sb . toString ( ) ; }
return vertex throwable as string compatible with the way tostring returns other information
