import pandas as pd
import os

class CSVSCache:
    def __init__(self, filename="results.csv"):
        self.filename = filename
        self.df = self._load_cache()

    def _load_cache(self):
        if os.path.exists(self.filename):
            return pd.read_csv(self.filename)
        return pd.DataFrame(columns=["task_id", "question", "answer"])

    def _save_cache(self):
        self.df.to_csv(self.filename, index=False)

    def get_all_entries(self):
        return self.df

def main():
    csv = CSVSCache()
    df = csv.get_all_entries()
    df['answers'].fillna("unknown", inplace=True)
    csv.df = df
    csv._save_cache()
if __name__ == "__main__":
    main()