'Initialize the class with a :class:`matplotlib.lines.Line2D`
instance.  The line should already be added to some
:class:`matplotlib.axes.Axes` instance and should have the
picker property set.'

def __init__(self, line):

    if (line.axes is None):
        raise RuntimeError(u'You    must    first    add    the    line    to    the    Axes')
    if (line.get_picker() is None):
        raise RuntimeError(u'You    must    first    set    the    picker    property    of    the    line')
    self.axes = line.axes
    self.line = line
    self.canvas = self.axes.figure.canvas
    self.cid = self.canvas.mpl_connect(u'pick_event', self.onpick)
    self.ind = set()
