How to use the railroad-diagrams.Skip function in railroad-diagrams

<div>
										order the result by the first column (default is ascending) and the second column descending:
										<code>τ [1], firstname desc (π id, firstname ( Customer ) )</code>
									</div>

									<div>
										
									</div>
								
							

							<div>
								<h4 id="relalg-operations-groupby">group by</h4>
								<table></table></div>

if (production.repetition && production.skippable === false) {
    return production.repeater
      ? OneOrMore(
          productionToDiagram(production.repetition, options),
          productionToDiagram(production.repeater, options)
        )
      : OneOrMore(productionToDiagram(production.repetition, options));
  }
  if (production.repetition && production.amount !== undefined) {
    return OneOrMore(
      productionToDiagram(production.repetition, options),
      Comment(`${production.amount} ×`, {})
    );
  }
  if (production.optional) {
    return Choice(1, Skip(), productionToDiagram(production.optional, options));
  }
  if (production.comment) {
    return production.group
      ? Sequence(
          productionToDiagram(production.group, options),
          Comment(production.comment, {})
        )
      : Comment(production.comment, {});
  }
  if (production.group) {
    return productionToDiagram(production.group, options);
  }
  if (production.exceptNonTerminal) {
    return NonTerminal(
      `${production.include} - ${production.exceptNonTerminal}`,
      {}