How to use the opencensus.trace.ext.grpc.client_interceptor.OpenCensusClientInterceptor function in opencensus

def test__intercept_call_metadata_none(self):
        tracer = mock.Mock()
        tracer.span_context = mock.Mock()
        test_header = 'test header'
        mock_propagator = mock.Mock()
        mock_propagator.to_header.return_value = test_header

        interceptor = client_interceptor.OpenCensusClientInterceptor(
            tracer=tracer, host_port='test')
        interceptor._propagator = mock_propagator
        mock_client_call_details = mock.Mock()
        mock_client_call_details.metadata = None
        mock_client_call_details.method = '/hello'

        client_call_details, request_iterator, current_span =\
            interceptor._intercept_call(
                mock_client_call_details, mock.Mock(), 'unary_unary')

        expected_metadata = (('grpc-trace-bin', test_header), )

        self.assertEqual(expected_metadata, client_call_details.metadata)

def _stream_helper(self):
        continuation = mock.Mock()
        mock_response = iter([mock.Mock()])
        continuation.return_value = mock_response
        mock_tracer = mock.Mock()
        interceptor = client_interceptor.OpenCensusClientInterceptor(
            tracer=mock_tracer)
        interceptor._intercept_call = mock.Mock(
            return_value=(None, iter([mock.Mock()]), mock.Mock()))
        return interceptor, continuation, mock_tracer

def test__end_span_between_context(self):
        from opencensus.trace import execution_context

        current_span = mock.Mock()
        tracer = mock.Mock()
        interceptor = client_interceptor.OpenCensusClientInterceptor(
            tracer=tracer, host_port='test')
        interceptor._end_span_between_context(current_span)

        span_in_context = execution_context.get_current_span()

        self.assertEqual(span_in_context, current_span)
        self.assertTrue(tracer.end_span.called)

def _unary_helper(self):
        continuation = mock.Mock()
        mock_response = mock.Mock()
        continuation.return_value = mock_response
        interceptor = client_interceptor.OpenCensusClientInterceptor()
        interceptor._intercept_call = mock.Mock(
            return_value=(None, iter([mock.Mock()]), None))
        return interceptor, continuation, mock_response

def test__intercept_call_metadata_tuple(self):
        tracer = mock.Mock()
        tracer.span_context = mock.Mock()
        test_header = 'test header'
        mock_propagator = mock.Mock()
        mock_propagator.to_header.return_value = test_header

        interceptor = client_interceptor.OpenCensusClientInterceptor(
            tracer=tracer, host_port='test')
        interceptor._propagator = mock_propagator
        mock_client_call_details = mock.Mock()
        mock_client_call_details.metadata = (('test_key', 'test_value'), )
        mock_client_call_details.method = '/hello'

        client_call_details, request_iterator, current_span =\
            interceptor._intercept_call(
                mock_client_call_details, mock.Mock(), 'unary_unary')

        expected_metadata = (
            ('test_key', 'test_value'),
            ('grpc-trace-bin', test_header),
        )

        self.assertEqual(expected_metadata, client_call_details.metadata)

from logger import getJSONLogger
logger = getJSONLogger('recommendationservice-server')

if __name__ == "__main__":
    # get port
    if len(sys.argv) > 1:
        port = sys.argv[1]
    else:
        port = "8080"

    try:
        exporter = stackdriver_exporter.StackdriverExporter()
        tracer = Tracer(exporter=exporter)
        tracer_interceptor = client_interceptor.OpenCensusClientInterceptor(tracer, host_port='localhost:'+port)
    except:
        tracer_interceptor = client_interceptor.OpenCensusClientInterceptor()

    # set up server stub
    channel = grpc.insecure_channel('localhost:'+port)
    channel = grpc.intercept_channel(channel, tracer_interceptor)
    stub = demo_pb2_grpc.RecommendationServiceStub(channel)
    # form request
    request = demo_pb2.ListRecommendationsRequest(user_id="test", product_ids=["test"])
    # make call to server
    response = stub.ListRecommendations(request)
    logger.info(response)