def line(self, x=None, y=None, **kwds):
return self(kind='<STR_LIT>', x=x, y=y, **kwds)<EOL>
Plot DataFrame columns as lines.

This function is useful to plot lines using DataFrame's values
as coordinates.

Parameters
----------
x : int or str, optional
    Columns to use for the horizontal axis.
    Either the location or the label of the columns to be used.
    By default, it will use the DataFrame indices.
y : int, str, or list of them, optional
    The values to be plotted.
    Either the location or the label of the columns to be used.
    By default, it will use the remaining DataFrame numeric columns.
**kwds
    Keyword arguments to pass on to :meth:`DataFrame.plot`.

Returns
-------
:class:`matplotlib.axes.Axes` or :class:`numpy.ndarray`
    Return an ndarray when ``subplots=True``.

See Also
--------
matplotlib.pyplot.plot : Plot y versus x as lines and/or markers.

Examples
--------

.. plot::
    :context: close-figs

    The following example shows the populations for some animals
    over the years.

    >>> df = pd.DataFrame({
    ...    'pig': [20, 18, 489, 675, 1776],
    ...    'horse': [4, 25, 281, 600, 1900]
    ...    }, index=[1990, 1997, 2003, 2009, 2014])
    >>> lines = df.plot.line()

.. plot::
   :context: close-figs

   An example with subplots, so an array of axes is returned.

   >>> axes = df.plot.line(subplots=True)
   >>> type(axes)
   <class 'numpy.ndarray'>

.. plot::
    :context: close-figs

    The following example shows the relationship between both
    populations.

    >>> lines = df.plot.line(x='pig', y='horse')