system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
/// @notice Retrieve the total number of NFTs owned by a specific address.
/// @dev NFTs associated with the zero address are invalid, and this function reverts if the zero address is queried.
/// @param _owner The address whose NFT balance is to be checked.
/// @return The count of NFTs held by _owner, which may be zero.

function balanceOf(address _owner) external view returns (uint256);
assistant
/// @notice postcondition _ownedTokensCount[_owner] == balance
function balanceOf(address _owner) public view returns (uint256 balance);
