input: Write a function to implement a TicTacToe game in Python. The function should include methods for initializing the game board, displaying the board, and checking if a player has won. The board should be a 3x3 grid, and the game should allow each player to place their mark ('x' or 'o') in turns.
  
  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().check_win() == False
  assert TicTacToe().check_win() == False
  assert TicTacToe().check_win() == False
  assert TicTacToe().check_win() == False
  assert TicTacToe().check_win() == False
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
  
      # 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
  