how to discard nodes has same values as earlier nodes in xml using xslt

my xml is as follows:

<?xml version="1.0" encoding="ISO-8859-1"?>
<?xml-stylesheet type="text/xsl" href="document-library-filter.xsl"?>
<xml total="14">
    <document>
        
        <file_type><![CDATA[application/pdf]]></file_type>
        <file_size><![CDATA[4420 KB]]></file_size>
        <document_group><![CDATA[LED Systems 1]]></document_group>
        
    </document>
    <document>
        
        <file_type><![CDATA[application/pdf]]></file_type>
        <file_size><![CDATA[4420 KB]]></file_size>
        <document_group><![CDATA[LED Systems 1]]></document_group>
        
  </xml>

it contains multiple document node. and each document node has file type node. value is pdf for all document nodes. i want to write out single file type node. and discard other nodes as they has same values. to do that i try to write out following xslt. but it writes out all the nodes.

following is the xslt:

<xsl:stylesheet version="1.0" xmlns:xsl="http://ift.tt/tCZ8VR">

        <xsl:output method="xml" indent="yes"/>
        
        <xsl:template match="/">
                
                <hr class="grid-hr inner-grid"/>
      <fieldset>
                        <legend>%%filter-file-types%%:</legend>
                        <ul class="itembrowser-filter">
                                <xsl:for-each select="xml/document">
                                        <xsl:if test="file_type">
                                                <xsl:variable name="file_type">
                                                        <xsl:value-of select="file_type"/>
                                                </xsl:variable>
                                                <xsl:variable name="file_type_Value">
                                                        <xsl:value-of select="substring-after($file_type,'/')"/>
                                                </xsl:variable>
                                                <li>
                                                        <label>
                                                                <input type="checkbox" class="input-big-checkbox" name="filetype-filter" value="{$file_type}"/>
                                                                <span class="label"><xsl:copy-of select="$file_type_Value" /></span>
                                                        </label>
                                                </li>
                                        </xsl:if>
                                </xsl:for-each>
                        </ul>
                </fieldset>
        <hr class="grid-hr inner-grid"/>
        </xsl:template>

i need some way to compare both the node values and if they are same then it will write out only once.

my expected output is:

<fieldset>
                        <legend>%%filter-file-types%%:</legend>
                        <ul class="itembrowser-filter">
                <li>
                  <label>
                    <input type="checkbox" class="input-big-checkbox" name="filetype-filter" value="application/pdf"/>
                    <span class="label"><xsl:copy-of select="pdf" /></span>
                  </label>
                </li>
              </ul>
  </fieldset>

i am not able to achieve this. please help me out.