docs: def add_series(self, series):
          """Adds a :py:class:`.Series` to the chart.
  
          :param Series series: The :py:class:`.Series` to add."""
  
          if not isinstance(series, Series):
              raise TypeError("'%s' is not a Series" % str(series))
          self._all_series.append(series)
          series._chart = self