class_docstr: Series Accessor & Method for creating Vega-Lite visualizations.
  
  Examples
  --------
  >>> s.vgplot.line()  # doctest: +SKIP
  >>> s.vgplot.area()  # doctest: +SKIP
  >>> s.vgplot.bar()  # doctest: +SKIP
  >>> s.vgplot.barh()  # doctest: +SKIP
  >>> s.vgplot.hist()  # doctest: +SKIP
  >>> s.vgplot.kde()  # doctest: +SKIP
  >>> s.vgplot.density()  # doctest: +SKIP
  
  Plotting methods can also be accessed by calling the accessor as a method
  with the ``kind`` argument: ``s.vgplot(kind='line', **kwds)``
  is equivalent to ``s.vgplot.line(**kwds)``
docstr: Line plot for Series data
  
  >>> series.vgplot.line()  # doctest: +SKIP
  
  Parameters
  ----------
  alpha : float, optional
      transparency level, 0 <= alpha <= 1
  width : int, optional
      the width of the plot in pixels
  height : int, optional
      the height of the plot in pixels
  ax: altair.Chart, optional
      chart to be overlayed with this vis (convinience method for `chart1 + chart2`)
  
  Returns
  -------
  chart : altair.Chart
      The altair plot representation
docstr_tok: ["Line","plot","for","Series","data",">",">",">","series.vgplot.line","(",")","#","doctest",":","+SKIP","Parameters","--","--","--","--","--","alpha",":","float",",","optional","transparency","level",",","0","<","=","alpha","<","=","1","width",":","int",",","optional","the","width","of","the","plot","in","pixels","height",":","int",",","optional","the","height","of","the","plot","in","pixels","ax",":","altair.Chart",",","optional","chart","to","be","overlayed","with","this","vis","(","convinience","method","for","`","chart1","+","chart2","`",")","Returns","--","--","--","-","chart",":","altair.Chart","The","altair","plot","representation"]
code: def line(self, alpha=None, width=450, height=300, ax=None, **kwds):
      """Line plot for Series data
  
      >>> series.vgplot.line()  # doctest: +SKIP
  
      Parameters
      ----------
      alpha : float, optional
          transparency level, 0 <= alpha <= 1
      width : int, optional
          the width of the plot in pixels
      height : int, optional
          the height of the plot in pixels
      ax: altair.Chart, optional
          chart to be overlayed with this vis (convinience method for `chart1 + chart2`)
  
      Returns
      -------
      chart : altair.Chart
          The altair plot representation
      """
      df = self._data.reset_index()
      df.columns = map(str, df.columns)
      x, y = df.columns
  
      chart = self._plot(
          data=df,
          width=width,
          height=height,
          title=kwds.pop("title", ""),
          figsize=kwds.pop("figsize", None),
          dpi=kwds.pop("dpi", None),
      )
  
      chart = chart.mark_line().encode(x=_x(x, df), y=_y(y, df))
  
      if alpha is not None:
          assert 0 <= alpha <= 1
          chart = chart.encode(opacity=alt.value(alpha))
  
      if ax is not None:
          return ax + chart
  
      warn_if_keywords_unused("line", kwds)
      return chart
  
imports: import numpy
  import pandas
  import altair
  from ._utils import infer_vegalite_type, unpivot_frame, warn_if_keywords_unused, validate_aggregation
  from ._pandas_internals import PandasObject, register_dataframe_accessor, register_series_accessor
label_desc: Use image node_id 2 for calling the SeriesPlotMethods obj's underlying member method code with example usage: obj.line(alpha, width, height, ax) and returns: chart, unknown