code: def to_df(self) -> pd.DataFrame:
          
          df = pd.DataFrame(index=RangeIndex(0, self.shape[0], name=None))
          for key in self.keys():
              value = self[key]
              for icolumn, column in enumerate(value.T):
                  df['{}{}'.format(key, icolumn+1)] = column
          return df
docs: Convert to pandas dataframe.