code: def read_dependent_peptides(filename):
      
      df = (pd.read_perseus(filename, usecols=_cols)
              .dropna(subset=['DP Ratio mod/base']))
      df['DP Ratio mod/base'] = df['DP Ratio mod/base'].astype(float)
      dep = df.pivot_table('DP Ratio mod/base', index=_index_columns,
                  columns='Raw file', aggfunc=np.median)
      localization = _count_localizations(df)
      return dep, localization
docs: read the dependent peptides table and extract localiztion information
      :param filename: path to the 'allPeptides.txt' table.
      :returns dep, localization: the dependent peptide table, localization information.