<?xml version="1.0" ?>
<sdf version='1.7'>
  <model name="model_frame_attached_to_nested_model">
    <link name="link"/>
    <model name="nested_model">
      <link name="nested_link"/>
    </model>
    <frame name="F1" attached_to="nested_model"/> <!-- VALID: Directly attached_to nested_model. -->
    <frame name="F2" attached_to="F1"/>           <!-- VALID: Indirectly attached_to nested_model. -->
  </model>
</sdf>
