code: def _set_contents(self, force=False):
          
  
          if self.children is None:
              self._parse_children()
  
          contents = BytesIO()
          for index, info in enumerate(self._fields):
              child = self.children[index]
              if child is None:
                  child_dump = b''
              elif child.__class__ == tuple:
                  if force:
                      child_dump = self._lazy_child(index).dump(force=force)
                  else:
                      child_dump = child[3] + child[4] + child[5]
              else:
                  child_dump = child.dump(force=force)
              # Skip values that are the same as the default
              if info[2] and 'default' in info[2]:
                  default_value = info[1](**info[2])
                  if default_value.dump() == child_dump:
                      continue
              contents.write(child_dump)
          self._contents = contents.getvalue()
  
          self._header = None
          if self._trailer != b'':
              self._trailer = b''
docs: Updates the .contents attribute of the value with the encoded value of
          all of the child objects
  
          :param force:
              Ensure all contents are in DER format instead of possibly using
              cached BER-encoded data