'Parameters
offset : pair of floats
The offset to apply to the path, in points.
shadow_color : color
The shadow color. Default is black.
A value of ``None`` takes the original artist\'s color
with a scale factor of `rho`.
alpha : float
The alpha transparency of the created shadow patch.
Default is 0.3.
rho : float
A scale factor to apply to the rgbFace color if `shadow_rgbFace`
is ``None``. Default is 0.3.
**kwargs
Extra keywords are stored and passed through to
:meth:`AbstractPathEffect._update_gc`.'

def __init__(self, offset=(2, (-2)), shadow_color=u'k', alpha=0.3, rho=0.3, **kwargs):

    super(SimpleLineShadow, self).__init__(offset)
    if (shadow_color is None):
        self._shadow_color = shadow_color
    else:
        self._shadow_color = mcolors.to_rgba(shadow_color)
    self._alpha = alpha
    self._rho = rho
    self._gc = kwargs
    self._offset_tran = mtransforms.Affine2D()
