code: def update(self, sums):
          
          for version in sums:
              hashes = sums[version]
              for filename in hashes:
                  hsh = hashes[filename]
                  file_xpath = './files/*[@url="%s"]' % filename
                  try:
                      file_add = self.root.findall(file_xpath)[0]
                  except IndexError:
                      raise ValueError("Attempted to update element '%s' which doesn't exist" % filename)
  
                  # Do not add duplicate, equal hashes.
                  if not self.version_exists(file_add, version, hsh):
                      new_ver = ET.SubElement(file_add, 'version')
                      new_ver.attrib = {
                              'md5': hsh,
                              'nb': version
                      }
docs: Update self.et with the sums as returned by VersionsX.sums_get
          @param sums: {'version': {'file1':'hash1'}}