input: Write a python function to print a matrix.
  assert printMatrix([["X", "O","X"], ["X", "O","X"]])==None
  assert printMatrix([["1", "2"], ["3", "4"]])==None
  assert printMatrix([["A", "B", "C"], ["D", "E", "F"], ["G", "H", "I"]])==None
output: def printMatrix(matrix):
      for row in matrix:
          print(" ".join(row))