code: def drop_stub_rows(self, ignore_cols=('specimen',
                                            'sample',
                                            'software_packages',
                                            'num')):
          
          # ignore citations if they just say 'This study'
          if 'citations' in self.df.columns:
              if list(self.df['citations'].unique()) == ['This study']:
                  ignore_cols = ignore_cols + ('citations',)
          drop_cols = self.df.columns.difference(ignore_cols)
          self.df.dropna(axis='index', subset=drop_cols, how='all', inplace=True)
          return self.df
docs: Drop self.df rows that have only null values,
          ignoring certain columns.
  
          Parameters
          ----------
          ignore_cols : list-like
              list of column names to ignore for
  
          Returns
          ---------
          self.df : pandas DataFrame