How to use the @phensley/cldr-ext-rbnf/lib/rbnftypes.Opcode.OPTIONAL function in @phensley/cldr-ext-rbnf

}

        case 'cardinal':
        case 'ordinal': {
          const block: any[] = [];
          for (const n of node.n) {
            const cat = PLURALS.indexOf(n.category);
            const i = symbols.indexOf(n.n);
            block.push([cat, i]);
          }
          return node.kind === 'cardinal' ? [Opcode.CARDINAL, block] : [Opcode.ORDINAL, block];
        }

        case 'optional': {
          const block = node.n.map(n => this.encodeNode(n, symbols));
          return [Opcode.OPTIONAL, block];
        }

        case 'sub-left':
          return [Opcode.SUB_LEFT];

        case 'sub-right':
          return [Opcode.SUB_RIGHT];

        case 'sub-right-3':
          return [Opcode.SUB_RIGHT_3];
      }
      throw new Error(`No encoder for node: ${JSON.stringify(node)}`);
  }