code: def _bss_decomp_mtifilt(reference_sources, estimated_source, j, C, Cj):
      
      filters_len = Cj.shape[-2]
  
      # zero pad
      s_true = _zeropad(reference_sources[j], filters_len - 1, axis=0)
  
      # compute appropriate projections
      e_spat = _project(reference_sources[j], Cj) - s_true
      e_interf = _project(reference_sources, C) - s_true - e_spat
      e_artif = - s_true - e_spat - e_interf
      e_artif[:estimated_source.shape[0], :] += estimated_source
  
      return (s_true, e_spat, e_interf, e_artif)
docs: Decomposition of an estimated source image into four components
      representing respectively the true source image, spatial (or filtering)
      distortion, interference and artifacts, derived from the true source
      images using multichannel time-invariant filters.