docs: def apply_units_to_cache(self, data):
          """
          Apply units to data read using :class:`JSONReader`.
  
          :param data: cached data
          :return: data with units applied
          :rtype: :class:`~pint.unit.Quantity`
          """
          for k, val in self.parameters.iteritems():
              if 'units' in val:
                  data[k] = Q_(data[k], val.get('units'))
          return data