input: Write a python function to multiply a 3x3 matrix with a scalar value.
  assert scalar_multiply([[3,6,2],[9,2,3],[4,8,6]], 3) == [[9,18,6],[27,6,9],[12,24,18]]
  assert scalar_multiply([[1,2,3],[4,5,6],[7,8,9]], 2) == [[2,4,6],[8,10,12],[14,16,18]]
  assert scalar_multiply([[0,0,0],[0,0,0],[0,0,0]], 5) == [[0,0,0],[0,0,0],[0,0,0]]
output: def scalar_multiply(matrix, scalar):
      return [[element * scalar for element in row] for row in matrix]