get(parentId, id, params) {
    const url = this.buildUrl(parentId, id, params);
    return this.shopify.request(url, 'GET', this.key);
  }
Get a single record by its ID.

@param {Number} parentId Parent record ID
@param {Number} id Record ID
@param {Object} [params] Query parameters
@return {Promise} Promise that resolves with the result
@public