code: def scale(self, sx, sy, sz):
          
          mat = numpy.array([
              [sx, 0, 0, 0],
              [0, sy, 0, 0],
              [0, 0, sz, 0],
              [0, 0, 0, 1]
          ])
          self.vectors = self.vectors.dot(mat)
          return self
docs: Scale mesh
  
          :param float sx: Amount to scale for x-direction
          :param float sy: Amount to scale for y-direction
          :param float sz: Amount to scale for z-direction