docs: def apply_units_to_cache(self, data):
          """
          Applies units to data when a proxy reader is used. For example if the
          data is cached as JSON and retrieved using the
          :class:`~simkit.core.data_readers.JSONReader`, then units can be
          applied from the original parameter schema.
  
          :param data: Data read by proxy reader.
          :return: data with units applied
          """
          # if units key exists then apply
          for k, v in self.parameters.iteritems():
              if v and v.get('units'):
                  data[k] = Q_(data[k], v.get('units'))
          return data