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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def set_proto_annotation(pb_annotation, span_data_annotation):
 """Sets properties on the protobuf Span annotation. :type pb_annotation: :class: `~opencensus.proto.trace.Span.TimeEvent.Annotation` :param pb_annotation: protobuf annotation :type span_data_annotation: :class: `~opencensus.trace.time_event.Annotation` :param span_data_annotation: opencensus annotation """


    pb_annotation.description.value = span_data_annotation.description
    if span_data_annotation.attributes is not None \
            and span_data_annotation.attributes.attributes is not None:
        for attribute_key, attribute_value in \
                span_data_annotation.attributes.attributes.items():
            add_proto_attribute_value(
                pb_annotation.attributes,
                attribute_key,
                attribute_value)