input: Write a python function to print out a matrix of numbers.
  assert print_matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) == None
  assert print_matrix([[1, 22, 333], [4444, 55, 6], [7, 8888, 99]]) == None
  assert print_matrix([[0]]) == None
output: def print_matrix(matrix):
      for row in matrix:
          print(" ".join(map(str, row)))