docs: def transform(self, tables, table_metas=None, missing=None):
          """Apply all the saved transformers to `tables`.
  
          Args:
              tables(dict):   mapping of table names to `tuple` where each tuple is on the form
                              (`pandas.DataFrame`, `dict`). The `DataFrame` contains the table data
                              and the `dict` the corresponding meta information.
                              If not specified, the tables will be retrieved using the meta_file.
  
              table_metas(dict):  Full metadata file for the dataset.
  
              missing(bool):      Wheter or not use NullTransformer to handle missing values.
  
          Returns:
              dict: Map from `str` (table_names) to `pandas.DataFrame` (transformed data).
          """
  
          if missing is None:
              missing = self.missing
  
          else:
              self.missing = missing
              warnings.warn(DEPRECATION_MESSAGE.format('transform'), DeprecationWarning)
  
          transformed = {}
  
          for table_name in tables:
              table = tables[table_name]
  
              if table_metas is None:
                  table_meta = self.table_dict[table_name][1]
              else:
                  table_meta = table_metas[table_name]
  
              transformed[table_name] = self.transform_table(table, table_meta)
  
          return transformed