add testable example for exemplar filter

sdk/metric/example_test.go

@@ -13,6 +13,7 @@ import (
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/sdk/instrumentation"
 	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/exemplar"
 	"go.opentelemetry.io/otel/sdk/resource"
 	semconv "go.opentelemetry.io/otel/semconv/v1.26.0"
 )
@@ -240,3 +241,21 @@ func ExampleNewView_exponentialHistogram() {
 		metric.WithView(view),
 	)
 }
+
+func ExampleWithExemplarFilter_disabled() {
+	// Use exemplar.AlwaysOffFilter to disable exemplar collection.
+	_ = metric.NewMeterProvider(
+		metric.WithExemplarFilter(exemplar.AlwaysOffFilter),
+	)
+}
+
+func ExampleWithExemplarFilter_custom() {
+	// Create a custom filter function that only offers measurements if the
+	// context has an error.
+	customFilter := func(ctx context.Context) bool {
+		return ctx.Err() != nil
+	}
+	_ = metric.NewMeterProvider(
+		metric.WithExemplarFilter(customFilter),
+	)
+}