I need to use functions inside

umbraco.requestHandler

how can i refer to this Class

I am doing this
xmlns:umbraco.requestHandler="urn:umbraco.requestHandler"

in the following

<>
version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxml="urn:schemas-microsoft-com:xslt" xmlns:umbraco.requestHandler="urn:umbraco.requestHandler"
xmlns:umbraco.library="urn:umbraco.library" xmlns:Exslt.ExsltCommon="urn:Exslt.ExsltCommon" xmlns:Exslt.ExsltDatesAndTimes="urn:Exslt.ExsltDatesAndTimes" xmlns:Exslt.ExsltMath="urn:Exslt.ExsltMath" xmlns:Exslt.ExsltRegularExpressions="urn:Exslt.ExsltRegularExpressions" xmlns:Exslt.ExsltStrings="urn:Exslt.ExsltStrings" xmlns:Exslt.ExsltSets="urn:Exslt.ExsltSets"
exclude-result-prefixes="msxml umbraco.requestHandler umbraco.library Exslt.ExsltCommon Exslt.ExsltDatesAndTimes Exslt.ExsltMath Exslt.ExsltRegularExpressions Exslt.ExsltStrings Exslt.ExsltSets ">


But getting errorss

System.Xml.Xsl.XslTransformException: Cannot find the script or external object that implements prefix 'urn:umbraco.requestHandler'.

kinldy help