docs: def _add_scope_deco(self, start, end, parent_start, parent_end, base_color,
                          factor):
          """
          Adds a scope decoration that enclose the current scope
          :param start: Start of the current scope
          :param end: End of the current scope
          :param parent_start: Start of the parent scope
          :param parent_end: End of the parent scope
          :param base_color: base color for scope decoration
          :param factor: color factor to apply on the base color (to make it
              darker).
          """
          color = drift_color(base_color, factor=factor)
          # upper part
          if start > 0:
              d = TextDecoration(self.editor.document(),
                                 start_line=parent_start, end_line=start)
              d.set_full_width(True, clear=False)
              d.draw_order = 2
              d.set_background(color)
              self.editor.decorations.append(d)
              self._scope_decos.append(d)
          # lower part
          if end <= self.editor.document().blockCount():
              d = TextDecoration(self.editor.document(),
                                 start_line=end, end_line=parent_end + 1)
              d.set_full_width(True, clear=False)
              d.draw_order = 2
              d.set_background(color)
              self.editor.decorations.append(d)
              self._scope_decos.append(d)