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HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages afcontinue="BPM_Change_Management_Lifecycle.png|4084" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:BA Retap - Liquids Workflow.png" />
      <f ns="6" title="File:BA Retap - Solids Workflow.png" />
      <f ns="6" title="File:BA Retap Description 05-06-17.docx" />
      <f ns="6" title="File:BA Retap Description 05-06-17.pdf" />
      <f ns="6" title="File:BPMN-Claim-End-2-End-Flows.pdf" />
      <f ns="6" title="File:BPMN Model.png" />
      <f ns="6" title="File:BPMN Model Introduction.pdf" />
      <f ns="6" title="File:BPMN and eXtended BPMN Shapes.pdf" />
      <f ns="6" title="File:BPM Center of Excellence - Figure 1.png" />
      <f ns="6" title="File:BPM Change Management Lifecycle.pdf" />
    </allfileusages>
  </query>
</api>