title: add element in a existing xml file python
body: <p>I have a existing xml file as following:</p>
  
  <pre><code>&lt;vehicleTravelTimeMeasurements&gt;
          &lt;vehicleTravelTimeMeasurement name="ckkkkkkkkkk" no="2"&gt;
              &lt;start link="1" pos="3.864983"/&gt;
              &lt;end link="3" pos="23.275375"/&gt;
          &lt;/vehicleTravelTimeMeasurement&gt;
          &lt;vehicleTravelTimeMeasurement name="" no="3"&gt;
              &lt;start link="1" pos="3.864983"/&gt;
              &lt;end link="2" pos="13.275375"/&gt;
          &lt;/vehicleTravelTimeMeasurement&gt;
  &lt;/vehicleTravelTimeMeasurements&gt;
  </code></pre>
  
  <p>I am trying to construct the same format as shown above by using xml.etree.cElementTree, and add them into the xml correctly:</p>
  
  <pre><code>new = ET.Element("vehicleTravelTimeMeasurement", name = "kkk", no = "4")
  newsub1 =  ET.Element("start", link = "1", pos="3.88888")
  newsub2 = ET.Element("end",link = "3", pos = "3.88888")
  </code></pre>
  
  <p>could someone help me out with this?</p>
  
  <p>Thank you in advance!</p>