tests/clocks/output_attr_clock/golden.model.xml

<?xml version="1.0"?>
<models>
  <model name="BLOCK">
    <input_ports>
      <port name="a" />
      <port name="b"/>
    </input_ports>
    <output_ports>
      <port name="o" is_clock="1" />
    </output_ports>
  </model>
</models>