code: def _SparseMatrixMulGrad(op: ops.Operation, grad):
      """Gradient for sparse_matrix_mul op."""
      # input to sparse_matrix_mul is (A, B) with CSR A and dense B.
      # Output is CSR:
      #   C = A .* B
      del op
      del grad
      raise NotImplementedError
  
file_path: tensorflow-upstream/tensorflow/python/ops/linalg/sparse/sparse_csr_matrix_grad.py
imports: from tensorflow.python.framework import ops
  from tensorflow.python.framework import sparse_tensor
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import array_ops_stack
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import sparse_ops
  from tensorflow.python.ops.linalg.sparse import sparse_csr_matrix_ops
label_desc: Use image node_id 13 for calling a global function with example usage: _SparseMatrixMulGrad(op, grad) without return types