code: public OptionalSyntax where(Expression<?>... expression) {
  		for (Expression<?> exp : expression) {
  			getMessage().getOptional().add(exp.toString());
  			LOG.debug("expression: " + exp);
  		}
  		QueryMessage mess = getMessage();
  		return new OptionalSyntax(mess);
  	}
docs: Method to get the optional syntax for where operator
  
  @param expression the expression
  @return OptionalSyntax the optional syntax