'Increment *in place* the virtual Polygon\'s rotation by ccw angle.
See also: rotate method which moves the center.
>>> from sympy import Polygon, Point, pi
>>> r = Polygon(Point(0,0), 1, n=3)
>>> r.vertices[0]
Point2D(1, 0)
>>> r.spin(pi/6)
>>> r.vertices[0]
Point2D(sqrt(3)/2, 1/2)
See Also
rotation
rotate : Creates a copy of the RegularPolygon rotated about a Point'

def spin(self, angle):

    self._rot += angle
