Call to a member function batchGet() on a non-object - google-analytics

Question

I'm working on getting some google analytics api stats and am able to get metrics just fine using this...
$results = getResults($analytics, $profile->getId(), $value);
$rows = $results->getRows();
$myvalue = $rows[0][0];
echo "<b>$value:</b> ". round($myvalue, 0) ."</br>";
but the below code throws an error (see post title) when I call batchGet using same analytics object that works in above code. Unsure why or if there is an alternative way to get the dimension data I'm after.
$device = new Google_Service_AnalyticsReporting_Dimension();
$device->setName("ga:deviceCategory");
// Create the ReportRequest object.
$request = new Google_Service_AnalyticsReporting_ReportRequest();
$request->setDimensions(array($device));
$body = new Google_Service_AnalyticsReporting_GetReportsRequest();
$body->setReportRequests( array( $request) );
return $analytics->reports->batchGet( $body );
Here is how I instantiate the $analytics object
function getService()
{
// service account email, and relative location of your key file.
$service_account_email = 'email#gserviceaccount.com';
$key_file_location = 'pathto/file.p12';
// Create and configure a new client object.
$client = new Google_Client();
$client->setApplicationName("Analytics");
$analytics = new Google_Service_Analytics($client);
$key = file_get_contents($key_file_location);
$cred = new Google_Auth_AssertionCredentials(
$service_account_email,
array(Google_Service_Analytics::ANALYTICS_READONLY),
$key
);
$client->setAssertionCredentials($cred);
if($client->getAuth()->isAccessTokenExpired()) {
$client->getAuth()->refreshTokenWithAssertion($cred);
}
return $analytics;
}

Answer 1

Still don't know why batchGet throws an error, but the code below works and will return the deviceCategories.
$optParams = array(
'dimensions' => 'ga:deviceCategory',
'filters' => 'ga:medium==organic');
$devices = $analytics->data_ga->get(
'ga:'.$profile->getId(),
'2015-05-01',
'2015-05-15',
'ga:sessions',
$optParams);
print_r($devices);