system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
/// @notice Get the count of NFTs belonging to a particular address.
/// @dev Querying the zero address will throw an error, as it is invalid.
/// @param _owner Address to check for owned NFTs.
/// @return The number of NFTs currently held 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);
