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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_key_info_node(security_token):
 """Create the KeyInfo node for WSSE. Note that this currently only supports BinarySecurityTokens Example of the generated XML: <ds:KeyInfo Id="KI-24C56C5B3448F4BE9D141094243396829"> <wsse:SecurityTokenReference wsse11:TokenType="{{ BINARY_TOKEN_TYPE }}"> <wsse:Reference URI="#X509-24C56C5B3448F4BE9D141094243396828" ValueType="{{ BINARY_TOKEN_TYPE }}"/> </wsse:SecurityTokenReference> </ds:KeyInfo> """

    key_info = etree.Element(ns_id('KeyInfo', ns.dsns))

    sec_token_ref = etree.SubElement(
        key_info, ns_id('SecurityTokenReference', ns.wssens))
    sec_token_ref.set(
        ns_id('TokenType', ns.wssens), security_token.get('ValueType'))

    reference = etree.SubElement(sec_token_ref, ns_id('Reference', ns.wssens))
    reference.set('ValueType', security_token.get('ValueType'))
    reference.set('URI', '#%s' % security_token.get(WSU_ID))
    return key_info