子文档的猫鼬自定义验证

Question

我想验证子文档以检查它是否属于其中一个模式，即字符串的枚举之类的子单词，但对于子文档模式，是否可以在猫鼬中使用？

const mongoose = require("mongoose");

const metadataSchema = require("../schemas/metadataSchema");
const sizeSchema = require("../schemas/sizeSchema");
const fieldMaskSchema = require("../schemas/fieldMaskSchema");

const singlePageDocumentSchema = require("./singlePageDocumentSchema");
const twoSideDocumentSchema = require("./twoSideDocumentSchema");
const topBottomDocumentSchema = require("./topBottomDocumentSchema");

const templateSchema = new mongoose.Schema({
  id: {
    type: String,
    required: true
  },
  metadata: metadataSchema,
  pageSize: {
    type: sizeSchema,
    required: true
  },
  fieldMasks: [fieldMaskSchema],
  // TODO validation for pages
  pages: Should be one of [singlePageDocumentSchema, twoSideDocumentSchema, topBottomDocumentSchema]
});

module.exports = templateSchema;

当子文档应该是三种类型之一时，也许还有其他方法可以实现这种行为？