How to make xsl:key work in the current context?

Question

XSL & XSLT

There is a script snippet:

<xsl:apply-templates select="item1/item2[generate-id(.)=generate-id(key('DutyKey',item3))]">
  <xsl:sort order="ascending" select="item3"/>	
</xsl:apply-templates>

With the help of which I get rid of duplication of lines when displaying a table in the called template.
The xml itself looks like:

<item0>
  <item1>
    <item2>
      <item3>
      </item3>
    </item2>
    <item2>
      <item3>
      </item3>
    </item2>
  </item1>
</item0>

There can be several item0 elements - and this is the problem. The keys are built immediately for the entire document, and not for the current item1, and as a result, the table is filled only for the first item0.
How can I make key() generate keys for the current context only?