code: def calc_indices(self, shape):
          
          if len(shape) == 2:
              ny, nx = shape
          elif len(shape) == 3:
              ny, nx, nchan = shape
  
          inds = []
          for iy in range(ny):
              inds.extend([(ix, iy) for ix in range(nx)])
          self.conf.indices = np.array(inds)
docs: calculates and stores the set of indices
          ix=[0, nx-1], iy=[0, ny-1] for data of shape (nx, ny)