code: public SimpleQuery withEndCursor(String cursor) {
  		return withEndCursor(cursor == null? null : Cursor.fromWebSafeString(cursor));
  	}
docs: Set the serialized {@link Cursor} to use with this query.
  This method is equivalent to invoking
  withEndCursor(Cursor.fromWebsafeString(cursor)), but it also accepts null values
  @param cursor the web-safe serialized cursor value. If null, it will be ignored.
  @return this instance