unable to parse graphml file with elementtree

xml

<?xml version="1.0" encoding="UTF-8"?>
<graphml xmlns="http://ift.tt/QM36aN"  
    xmlns:xsi="http://ift.tt/ra1lAU"
    xsi:schemaLocation="http://ift.tt/1guo4q0">
  <graph id="G" edgedefault="undirected">
    <node id="n0"/>
    <node id="n1"/>
    <edge id="e1" source="n0" target="n1"/>
  </graph>
</graphml>

python code

tree = ET.parse(my_file.xml).getroot()

print tree.findall('graph') # returns []

If I remove the attributes from the graphml tag, then it works, returns the element