code: def data_response(self):
          
          d = []
          for i in range(self._num_bands):
              if self._compute_bool[i] is True:
                  d_i = self._imageModel_list[i].data_response
                  if d == []:
                      d = d_i
                  else:
                      d = np.append(d, d_i)
          return d
docs: returns the 1d array of the data element that is fitted for (including masking)
  
          :return: 1d numpy array