code: function getResponseHeaders (req) {
    let corsHeaders = {};
    if (req.swagger) {
      let headers = [];
  
      if (req.method !== "OPTIONS") {
        // This isn't a preflight request, so the operation's response headers take precedence over the OPTIONS headers
        headers = getOperationResponseHeaders(req.swagger.operation);
      }
  
      if (req.swagger.path) {
        // Regardless of whether this is a preflight request, append the OPTIONS response headers
        headers = headers.concat(getOperationResponseHeaders(req.swagger.path.options));
      }
  
      // Add the headers to the `corsHeaders` object.  First one wins.
      headers.forEach((header) => {
        if (corsHeaders[header.name] === undefined) {
          corsHeaders[header.name] = header.value;
        }
      });
    }
  
    return corsHeaders;
  }
docs: Returns an object containing the CORS response headers that are defined in the Swagger API.
  If the same CORS header is defined for multiple responses, then the first one wins.
  
  @param   {Request}   req
  @returns {object}