celery: use self helper to retrieve metrics for assertion (#4124)

* celery: use self helper to retrieve metrics for assertion

* Manual formatting

Author: anuraaga

instrumentation/opentelemetry-instrumentation-celery/tests/test_metrics.py

@@ -71,43 +71,22 @@ def test_basic_metric(self):
     def test_metric_uninstrument(self):
         CeleryInstrumentor().instrument()
 
-        self.get_metrics()
+        metrics = self.get_metrics()
         self.assertEqual(
-            (
-                self.memory_metrics_reader.get_metrics_data()
-                .resource_metrics[0]
-                .scope_metrics[0]
-                .metrics[0]
-                .data.data_points[0]
-                .bucket_counts[1]
-            ),
+            metrics[0].data.data_points[0].bucket_counts[1],
             1,
         )
 
-        self.get_metrics()
+        metrics = self.get_metrics()
         self.assertEqual(
-            (
-                self.memory_metrics_reader.get_metrics_data()
-                .resource_metrics[0]
-                .scope_metrics[0]
-                .metrics[0]
-                .data.data_points[0]
-                .bucket_counts[1]
-            ),
+            metrics[0].data.data_points[0].bucket_counts[1],
             2,
         )
 
         CeleryInstrumentor().uninstrument()
 
-        self.get_metrics()
+        metrics = self.get_metrics()
         self.assertEqual(
-            (
-                self.memory_metrics_reader.get_metrics_data()
-                .resource_metrics[0]
-                .scope_metrics[0]
-                .metrics[0]
-                .data.data_points[0]
-                .bucket_counts[1]
-            ),
+            metrics[0].data.data_points[0].bucket_counts[1],
             2,
         )