code: def _set_contents(self, force=False):
          
  
          if self.children is None:
              self._parse_children()
  
          child_encodings = []
          for child in self:
              child_encodings.append(child.dump(force=force))
  
          self._contents = b''.join(sorted(child_encodings))
          self._header = None
          if self._trailer != b'':
              self._trailer = b''
docs: Encodes all child objects into the contents for this object.
  
          This method is overridden because a SetOf needs to be encoded by
          sorting the child encodings.
  
          :param force:
              Ensure all contents are in DER format instead of possibly using
              cached BER-encoded data