Using code i pull values from xml and put it into a hashes then put it back
into xml to get the unique set. However, I was wondering if this was
possible via xsl:

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<foo>
       <bars type="bartype">
            <bar id="1" x="a1" y="a2" z="3"/>
            <bar id="2" x="a11" y="a22" z="33"/>
            <bar id="1" x="a11111" y="a22222" z="33333"/>
        </bars>
        <houses type="housetype">
            <house id="7" a="a1" b="a2" c="a3"/>
            <house id="8" a="a1" b="a2" c="a3"/>
            <house id="9" a="a1" b="a2" c="a3"/>
        </houses>
       <bars type="bartype">
            <bar id="2" x="a111" y="a222" z="a333"/>
            <bar id="1" x="a1111" y="a2222" z="a3333"/>
        </bars>
</foo>
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to
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<uniques>
    <unique id="1" type="bartype"/>
    <unique id="2" type="bartype"/>
    <unique id="7" type="housetype"/>
    <unique id="8" type="housetype"/>
    <unique id="9" type="housetype"/>
</uniques>
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