function getJsonContentType (contentObj) {
  let jsonContentType = _.find(_.keys(contentObj), (contentType) => {
    let mediaType = parseMediaType(contentType);

    return mediaType.type === 'application' && (
      mediaType.subtype === 'json' || _.endsWith(mediaType.subtype, '+json')
    );
  });

  return jsonContentType;
}
Finds valid JSON media type object from content object

@param {*} contentObj - Content Object from schema
@returns {*} - valid JSON media type if exists