func: function removeNFToken(
      address _from,
      uint256 _tokenId
    )
     internal
    {
      require(idToOwner[_tokenId] == _from);
      assert(ownerToNFTokenCount[_from] > 0);
      ownerToNFTokenCount[_from] = ownerToNFTokenCount[_from] - 1;
      delete idToOwner[_tokenId];
    }