AttributeError: 'SubscriberClient' object has no attribute 'transport' error while reading from input subscription with ReadFromPubSub

When I read from the input-subcroption with beam.io.ReadFromPubSub. The error below is thrown.

 AttributeError: 'SubscriberClient' object has no attribute 'transport'

Code

pipeline_options = PipelineOptions()
pipeline_options.view_as(StandardOptions).streaming = True

pipeline = beam.Pipeline(options=pipeline_options)
messages = (pipeline | beam.io.ReadFromPubSub(subscription=input_subscription).with_output_types(bytes))

def printattr(element):
{{ print(element.attributes)}}

lines = messages | 'printattr' >> beam.Map(printattr)

result = pipeline.run()
result.wait_until_finish()