code: function default_headers(class_context) {
    class_context = class_context || {};
    let headers   = {};
  
    if (class_context.token) {
      headers.Token = class_context.token;
    }
  
    if (!isBrowser) {
      headers['User-Agent'] = `Tago-Nodelib-${pkg.version}`;
    }
  
    return headers;
  }
docs: default_headers
  Generate default headers
  @private
  @return {JSON}