You are looking at the HTML representation of the XML format.
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 gafcontinue="SR_Siddhasana.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="90" ns="6" title="File:Basic Tenets of Patanjala Yoga Ramaswami.cover-v3.png" />
      <page pageid="17" ns="6" title="File:CA7EMHZV-800x600.jpg" />
      <page pageid="13" ns="6" title="File:Cd1.gif" />
      <page pageid="14" ns="6" title="File:Cd2.gif" />
      <page pageid="15" ns="6" title="File:Cd3.gif" />
      <page pageid="62" ns="6" title="File:Complete book cover.gif" />
      <page pageid="8" ns="6" title="File:Ganapathi.gif" />
      <page pageid="5" ns="6" title="File:IMGP1166.JPG" />
      <page pageid="79" ns="6" title="File:IMG 0019.jpg" />
      <page pageid="81" ns="6" title="File:SR Badri 2015.jpg" />
    </pages>
  </query>
</api>