class_docstr: <<< ThemeRiver >>>
  
  ThemeRiver graph is a special kind of flow graph,
  which is mainly used to show the changes of events or themes
  over a period of time.
code: def add(
      self,
      series_name: types.Sequence,
      data: types.Sequence[types.Union[opts.ThemeRiverItem, dict]],
      *,
      label_opts: types.Label = opts.LabelOpts(),
      singleaxis_opts: types.SingleAxis = opts.SingleAxisOpts(),
      tooltip_opts: types.Tooltip = None,
      itemstyle_opts: types.ItemStyle = None,
  ):
      for n in series_name:
          self._append_legend(n)
  
      self.options.get("series").append(
          {
              "type": ChartType.THEMERIVER,
              "name": series_name,
              "data": data,
              "label": label_opts,
              "tooltip": tooltip_opts,
              "itemStyle": itemstyle_opts,
          }
      )
  
      self.options.update(singleAxis=singleaxis_opts)
      self.options.get("tooltip").update(trigger="axis")
      return self
  
imports: from ...None import options
  from ...None import types
  from ...charts.chart import Chart
  from ...globals import ChartType
label_desc: Use image node_id 1 for calling the ThemeRiver obj's underlying member method code with example usage: obj.add(series_name, data) and returns: self