<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def df_all(self, phot):
 """Subclasses may want to sort this """

        df = pd.concat([self.to_df(f) for f in self.get_filenames(phot)])
        return df