code: private <RequestT, ResponseT> UnaryCallable<RequestT, ResponseT> createUserFacingUnaryCallable(
        String methodName, UnaryCallable<RequestT, ResponseT> inner) {
  
      UnaryCallable<RequestT, ResponseT> traced =
          new TracedUnaryCallable<>(
              inner,
              clientContext.getTracerFactory(),
              SpanName.of(TRACING_OUTER_CLIENT_NAME, methodName));
  
      return traced.withDefaultCallContext(clientContext.getDefaultCallContext());
    }
docs: Wraps a callable chain in a user presentable callable that will inject the default call context
  and trace the call.