code: def add_private_note(self, note, source=None):
          
          note = {
              'value': note,
          }
          if source:
              note['source'] = source
          self._append_to('_private_notes', note)
docs: Add a private note.
  
          Args:
              :param comment: comment about the author.
              :type comment: string
  
              :param source: the source of the comment.
              :type source: string