code: def _update_separator(self, offset):
          
          offset_line = self.handles['offset_line']
          if offset == 0:
              offset_line.set_visible(False)
          else:
              offset_line.set_visible(True)
              if self.invert_axes:
                  offset_line.set_xdata(offset)
              else:
                  offset_line.set_ydata(offset)
docs: Compute colorbar offset and update separator line
          if map is non-zero.