getNumReadonlySigners method
Counts the number of accounts that are signers and readonly.
Implementation
int getNumReadonlySigners() =>
    fold(0, (total, account) => total + (!account.isWriteable && account.isSigner ? 1 : 0));Counts the number of accounts that are signers and readonly.
int getNumReadonlySigners() =>
    fold(0, (total, account) => total + (!account.isWriteable && account.isSigner ? 1 : 0));