How to swap the headers in a request in wso2 API Manager

File Name: /_system/governance/apimgt/customsequences/in/auth_token_swapper.xml

Content: 
<sequence xmlns="http://ws.apache.org/ns/synapse" name="AuthToken--Swapper--In">

         <property name="Backend-Authorization" expression="$trp:Backend-Authorization" scope="default" type="STRING"/>

         <property name="TPaaS-Authorization" expression="$trp:Authorization" scope="default" type="STRING"/>

    <filter xpath="fn:string-length(get-property('Backend-Authorization')) > 0">

          <then>

              <property name="TPaaS-Authorization" expression="get-property('TPaaS-Authorization')" scope="transport"/>

              <property name="Authorization" expression="get-property('Backend-Authorization')" scope="transport"/>

              <log level="custom">

                  <property name="TRACE" value="Global Mediation Extension by Guru Authorization is there."/>

              </log>

          </then>

          <else>

              <log level="custom">

                  <property name="TRACE" value="Global Mediation Extension by Guru Authorization is not there."/>

              </log>

          </else>

     </filter>

</sequence>