<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _filter(self, filename: str, df: pd.DataFrame) -> pd.DataFrame: """Apply view filters"""

        view = self._view.get(filename)
        if view is None:
            return df

        for col, values in view.items():
            # If applicable, filter this dataframe by the given set of values
            if col in df.columns:
                df = df[df[col].isin(setwrap(values))]

        return df