docs: def clear_cached(self):
          """
          Remove any cached result of this column.
  
          """
          x = _COLUMN_CACHE.pop((self.table_name, self.name), None)
          if x is not None:
              logger.debug(
                  'cleared cached value for column {!r} in table {!r}'.format(
                      self.name, self.table_name))