'Returns the sketch parameters for the artist.
Returns
sketch_params : tuple or `None`
A 3-tuple with the following elements:
* `scale`: The amplitude of the wiggle perpendicular to the
source line.
* `length`: The length of the wiggle along the line.
* `randomness`: The scale factor by which the length is
shrunken or expanded.
May return `None` if no sketch parameters were set.'

def get_sketch_params(self):

    return self._sketch
