setUserAgent() public method

Set the user agent. It is a good ides to leave this as is.
public setUserAgent ( string $userAgent ) : Google\Spreadsheet\DefaultServiceRequest
$userAgent string
return Google\Spreadsheet\DefaultServiceRequest
 public function testSetUserAgent()
 {
     $request = new DefaultServiceRequest("token");
     $this->assertTrue($request->setUserAgent("my user agent") instanceof DefaultServiceRequest);
     $this->assertEquals("my user agent", $request->getUserAgent());
 }