Python: Why this error is coming?

With reference to this question: Python: In an xml, How to delete nodes within a parent node

Can anyone explain me why I'm facing this issue in my python script.

Value Error : list.remove(x): x not in list

Code below.

import xml.etree.cElementTree as ET

try:
   tree = ET.parse('Test.xml')
   root = tree.getroot()
   keeper_data = ['06354237', '87654321']
   instances = root.findall('./Replication/Instance')
   for instance in instances:
       data = instance.find('./DataSet/Data')
       if data.text not in keeper_data:
          root.remove(instance)

tree.write('New.xml')

except ValueError as err:
     print ('Value Error : ' + str(err))

xml sample below.Please note the only difference in xml structure from previous question is the addition of tag which encloses all the tags.

<?xml version='1.0' encoding='UTF-8'?>
<Root>
<Identification>
   <Description ID="12">Some text</Description>
</Identification>
<Symbols>
  <Name Width="1">abc</Name>
  <Name Width="2">def</Name>
</Symbols>
<Replication  iRowRef="884">
   <Instance RowRef="A">
      <DataSet>
          <Data>12345678</Data>
      </DataSet>
      <DataSet>
          <Data>abcd</Data>
      </DataSet>
      <DataSet>
          <Data>abcd</Data>
      </DataSet>
   </Instance>
   <Instance RowRef="B">
      <DataSet>
         <Data>87654321</Data>
      </DataSet>
      <DataSet>
         <Data>abcd</Data>
      </DataSet>
      <DataSet>
         <Data>abcd</Data>
      </DataSet>
   </Instance>
   <Instance RowRef="C">
      <DataSet>
         <Data>06354237</Data>
      </DataSet>
      <DataSet>
         <Data>abcd</Data>
      </DataSet>
      <DataSet>
         <Data>abcd</Data>
      </DataSet>
  </Instance>
</Replication>
</Root>