function approve(address spender, uint256 value) public whenNotPaused returns (bool) {
    require(spender != address(0));
    uint256 time = getLockTokenTime(msg.sender);
    uint256 blockTime = block.timestamp;
    require(blockTime >time);
    _allowed[msg.sender][spender] = value;
    emit Approval(msg.sender, spender, value);
    return true;
  }