var Converter = require('api-spec-converter');
Converter.convert({
  from: 'swagger_1',
  to: 'swagger_2',
  source: 'https://api.gettyimages.com/swagger/api-docs',
}, function(err, converted) {
  console.log(converted.stringify());
})

var Converter = require('api-spec-converter');
Converter.convert({
  from: 'swagger_1',
  to: 'swagger_2',
  source: 'https://api.gettyimages.com/swagger/api-docs',
}, function(err, converted) {

  // [Optional] Fill missing fields with dummy values
  converted.fillMissing();

  // [Optional] Validate converted spec
  converted.validate(function (errors, warnings) {
    if (errors)
      return console.error(JSON.stringify(errors, null, 2));
    if (warnings)
      return console.error(JSON.stringify(warnings, null, 2));

    console.log(converted.stringify());
    FS.writeFileSync('swagger2.json', converted.stringify());
  });
})

APISpecConverter.convert(...)