docs: def load_data(self, filename, *args, **kwargs):
          """
          Load parameterized data from different sheets.
          """
          # load parameterized data
          data = super(ParameterizedXLS, self).load_data(filename)
          # add parameter to data
          parameter_name = self.parameterization['parameter']['name']
          parameter_values = self.parameterization['parameter']['values']
          parameter_units = str(self.parameterization['parameter']['units'])
          data[parameter_name] = parameter_values * UREG(parameter_units)
          # number of sheets
          num_sheets = len(self.parameterization['parameter']['sheets'])
          # parse and concatenate parameterized data
          for key in self.parameterization['data']:
              units = str(self.parameterization['data'][key].get('units')) or ''
              datalist = []
              for n in xrange(num_sheets):
                  k = key + '_' + str(n)
                  datalist.append(data[k].reshape((1, -1)))
                  data.pop(k)  # remove unused data keys
              data[key] = np.concatenate(datalist, axis=0) * UREG(units)
          return data