static _parseAuditsList(auditsJson, pluginName) {
    // Plugin audits aren't required (relying on LH default audits) so fall back to [].
    if (auditsJson === undefined) {
      return undefined;
    } else if (!isArrayOfUnknownObjects(auditsJson)) {
      throw new Error(`${pluginName} has an invalid audits array.`);
    }

    return auditsJson.map(auditDefnJson => {
      const {path, ...invalidRest} = auditDefnJson;
      assertNoExcessProperties(invalidRest, pluginName, 'audit');

      if (typeof path !== 'string') {
        throw new Error(`${pluginName} has a missing audit path.`);
      }
      return {
        path,
      };
    });
  }
Extract and validate the list of AuditDefns added by the plugin (or undefined
if no additional audits are being added by the plugin).
@param {unknown} auditsJson
@param {string} pluginName
@return {Array<{path: string}>|undefined}