[xsl] Member function?

["Dave Pawson dave.pawson@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

xpath 2 or 3

I have a sort index
<d:sort_index name="my_sort">
    <d:entry key="Jan" index="0"/>
    <d:entry key="Feb" index="1"/>
    <d:entry key="Mar" index="2"/>
    <d:entry key="Apr" index="3"/>
    <d:entry key="May" index="4"/>
    <d:entry key="Jun" index="5"/>
    <d:entry key="Jul" index="6"/>
    <d:entry key="Aug" index="7"/>
    <d:entry key="Sep" index="8"/>
    <d:entry key="Oct" index="9"/>
    <d:entry key="Nov" index="10"/>
    <d:entry key="Dec" index="11"/>

  </d:sort_index>

  <xsl:variable name="sort_index" select="document('')//d:sort_index"/>

and xml with many

<book>
      <author>
        <f>H</f>
        <s>Stone</s>
      </author>
      <t>Jane Doe</t>
      <d>Jul 2018</d>
    </book>

I want to check that the d element (month) has an entry in the sort
index using xsl:for-each over //book/d

Suggestions please?

TiA


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Dave Pawson
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