code: def add(self, decorations):
          
          added = 0
          if isinstance(decorations, list):
              not_repeated = set(decorations) - set(self._decorations)
              self._decorations.extend(list(not_repeated))
              added = len(not_repeated)
          elif decorations not in self._decorations:
              self._decorations.append(decorations)
              added = 1
  
          if added > 0:
              self._order_decorations()
              self.update()
          return added
docs: Add text decorations on a CodeEditor instance.
  
          Don't add duplicated decorations, and order decorations according
          draw_order and the size of the selection.
  
          Args:
              decorations (sourcecode.api.TextDecoration) (could be a list)
          Returns:
              int: Amount of decorations added.