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>
    <alltransclusions gatcontinue="If:|7454" />
  </query-continue>
  <query>
    <pages>
      <page pageid="7454" ns="0" title="Bayesian Methods for Hackers" />
      <page pageid="11295" ns="0" title="UC Irvine Machine Learning Repository" />
      <page pageid="11301" ns="0" title="R Cookbook" />
      <page pageid="11307" ns="0" title="R Graphics Cookbook" />
      <page pageid="11309" ns="0" title="Python for Data Analysis" />
      <page pageid="11311" ns="0" title="Programming Collective Intelligence: Building Smart Web 2.0 Applications" />
      <page pageid="11313" ns="0" title="Agile Data Science" />
      <page pageid="11427" ns="0" title="PASCAL Visual Object Classes data sets" />
      <page pageid="12791" ns="0" title="Labeled Faces in the Wild" />
      <page pageid="13877" ns="0" title="LMFDB" />
    </pages>
  </query>
</api>