class_docstr: Compose lower triangular matrix.
class_docstr_tok: ["Compose","lower","triangular","matrix","."]
code: def backward(self, inputs, grad_outputs):
      diag, non_diag = inputs
      gy = grad_outputs[0]
      gdiag = _get_batch_diagonal(gy)
      gnon_diag = _get_batch_non_diagonal(gy)
      return gdiag, gnon_diag
  
imports: from functools import lru_cache
  from chainer import cuda
  from chainer import function
  from chainer.utils import type_check
  import numpy
label_desc: Use image node_id 4 for calling the LowerTriangularMatrix obj's underlying member method code with example usage: obj.backward(inputs, grad_outputs) and returns: gdiag,  gnon_diag