docs: def get_data(self, file_id):
          """
          Acquires the data from the table identified by the id.
  
          The file is read only once, consecutive calls to this method will
          return the sale collection.
  
          :param file_id: identifier for the table
          :return: all the values from the table
          """
          if file_id not in self._file_values:
              file_contents = 'cwr_%s.csv' % file_id
              self._file_values[file_id] = self._reader.read_csv_file(
                  file_contents)
  
          return self._file_values[file_id]