'Set or return the current shearfactor.
Optional argument: shear -- number, tangent of the shear angle
Shear the turtleshape according to the given shearfactor shear,
which is the tangent of the shear angle. DO NOT change the
turtle\'s heading (direction of movement).
If shear is not given: return the current shearfactor, i. e. the
tangent of the shear angle, by which lines parallel to the
heading of the turtle are sheared.
Examples (for a Turtle instance named turtle):
>>> turtle.shape("circle")
>>> turtle.shapesize(5,2)
>>> turtle.shearfactor(0.5)
>>> turtle.shearfactor()
>>> 0.5'

def shearfactor(self, shear=None):

    if (shear is None):
        return self._shearfactor
    self.pen(resizemode='user', shearfactor=shear)
