<?xml version="1.0" encoding="UTF-8"?>
<tube name="test">
  <lines>
    <line id="A" name="A" color="red"/>
  </lines>
  <stations>
    <station id="A1" name="A1" line="A:1" link="A2"   />
    <station id="A2" name="A2" line="A:2" link="A1,A3"/>
    <station id="A3" name="A3" line="A:3" link="" other_link="walk:A4"/>
    <station id="A4" name="A4" line="A:4" link="A2"/>
  </stations>
</tube>