How to use the yaml.defaultOptions function in yaml

'use strict';

const fs = require('fs');
const path = require('path');
const url = require('url');
const util = require('util');

const fetch = require('node-fetch');
const co = require('co');
const yaml = require('yaml');
yaml.defaultOptions.prettyErrors = true;
const jsy = require('js-yaml');
const bsc = require('swagger-parser');
const openapi3 = require('oas-validator');
const asyncApiSchema = require('asyncapi/schemas/1.2.0.json');
const ajv = require('ajv')({
    allErrors: true,
    verbose: true,
    jsonPointers: true
});
const recurse = require('reftools/lib/recurse').recurse;

//require("raml-1-parser/plugins/resourceUriValidationPlugin");
//require("raml-1-parser/plugins/crudAnnotationsValidator");
//require("raml-1-parser/plugins/uninheritedTypesDetector");
//require("raml-1-parser/plugins/xmlAnnotationsValidator");