input: Write a function to create a TicTacToe class in Python that initializes a 3x3 board, allows players to take turns placing their marks, and checks for a winning condition after each move. The board should be displayed after each move. The function should return None. 
  class TicTacToe:
     def __init__(self):
         self.board = [['_' for _ in range(3)] for _ in range(3)]
         self.turn = 'x'
         
     def display(self):
         for row in self.board:
             print(' '.join(row))
             
     def check_win(self):
         board = self.board
         # check if the player with the current turn has a row of three
         for row in self.board:
             if row.count(self.turn) == 3:
                 return True
             
         # check if the player with the current turn has a column of three
         for col in range(3):
             if board[0][col] == board[1][col] and board[1][col] == board[2][col] and board[2][col] == self.turn:
                 return True
             
         # check for the two diagonals
         if board[0][0] == board[1][1] and board[1][1] == board[2][2] and board[2][2] == self.turn:
             return True
         if board[0][2] == board[1][1] and board[1][1] == board[2][0] and board[2][0] == self.turn:
             return True
         return False
  assert TicTacToe() is not None
output: 
  def __init__(self):
      self.board = [['_' for _ in range(3)] for _ in range(3)]
      self.turn = 'x'
  
  def display(self):
      for row in self.board:
          print(' '.join(row))
  
  def check_win(self):
      board = self.board
      for row in self.board:
          if row.count(self.turn) == 3:
              return True
      for col in range(3):
          if board[0][col] == board[1][col] and board[1][col] == board[2][col] and board[2][col] == self.turn:
              return True
      if board[0][0] == board[1][1] and board[1][1] == board[2][2] and board[2][2] == self.turn:
          return True
      if board[0][2] == board[1][1] and board[1][1] == board[2][0] and board[2][0] == self.turn:
          return True
      return False
  