Add _is_instrumented_by_opentelemetry to the transport

Author: Kludex

instrumentation/opentelemetry-instrumentation-httpx/src/opentelemetry/instrumentation/httpx/__init__.py

@@ -402,6 +402,8 @@ class SyncOpenTelemetryTransport(httpx.BaseTransport):
             that is called right before the span ends
     """
 
+    _is_instrumented_by_opentelemetry = True
+
     def __init__(
         self,
         transport: httpx.BaseTransport,
@@ -527,6 +529,8 @@ class AsyncOpenTelemetryTransport(httpx.AsyncBaseTransport):
             that is called right before the span ends
     """
 
+    _is_instrumented_by_opentelemetry = True
+
     def __init__(
         self,
         transport: httpx.AsyncBaseTransport,