system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
/// @notice Determine how many NFTs are owned by a given address.
/// @dev This function reverts for the zero address since it cannot hold NFTs.
/// @param _owner The address to query for NFT ownership.
/// @return The total NFTs owned by _owner.

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