This method is called from the
response object. It returns a string of the additional response headers.
With server-side functions, you may occasionally want to operate on the HTTP responses your function returns. Using this method, you can retrieve the response headers. You may find this useful in situations where you need to log information from the response header or where you want to modify the value the function returns. To set the response to additional headers, see
var header = response.getHeader()
This method returns a string containing the additional headers in the response.