code: public Schema rowtime(Rowtime rowtime) {
  		if (lastField == null) {
  			throw new ValidationException("No field defined previously. Use field() before.");
  		}
  		tableSchema.get(lastField).putAll(rowtime.toProperties());
  		lastField = null;
  		return this;
  	}
docs: Specifies the previously defined field as an event-time attribute.
  
  <p>E.g. field("rowtime", Types.SQL_TIMESTAMP).rowtime(...)