input: Write a python function to create a TicTacToe class that initializes the board, prints it, and allows making a move.
  assert t = TicTacToe(); t.make_move(0, 0, 'X'); t.board == [['X', '-', '-'], ['-', '-', '-'], ['-', '-', '-']]
  assert t = TicTacToe(); t.make_move(1, 1, 'O'); t.board == [['-', '-', '-'], ['-', 'O', '-'], ['-', '-', '-']]
  assert t = TicTacToe(); t.make_move(2, 2, 'X'); t.board == [['-', '-', '-'], ['-', '-', '-'], ['-', '-', 'X']]
output: class TicTacToe:
      def __init__(self):
          self.board = [['-' for _ in range(3)] for _ in range(3)]
      
      def print_board(self):
          for row in self.board:
              print(' '.join(row))
      
      def make_move(self, row, col, player):
          if self.board[row][col] == '-':
              self.board[row][col] = player