code: def get_transformation_matrix(self, theta):
          
          ct = numpy.cos(theta + self.theta)
          st = numpy.sin(theta + self.theta)
          ca = numpy.cos(self.alpha)
          sa = numpy.sin(self.alpha)
  
          return numpy.matrix(((ct, -st * ca, st * sa, self.a * ct),
                               (st, ct * ca, -ct * sa, self.a * st),
                               (0, sa, ca, self.d),
                               (0, 0, 0, 1)))
docs: Computes the homogeneous transformation matrix for this link.