code: def get_grads(self, grad, need_grad_flags):
      ng_flags = [ng for ng in need_grad_flags if ng is not None]
      for ivar, ng in zip(self.input_dict.values(), ng_flags):
          ivar.need_grad = ng
          ivar.grad.zero()
      self.output.forward(clear_no_need_grad=True)
      self.output.backward(grad, clear_buffer=True)
      return np.concatenate(
          [
              ivar.grad.get_data("r").flatten()
              for (ivar, ng) in zip(self.input_dict.values(), ng_flags)
              if ng
          ]
      )
  
file_path: nnabla/python/test/function/test_fused_convolution.py
imports: import pytest
  import numpy
  import nnabla
  import nnabla.functions
  import nnabla.ext_utils
  from nbla_test_utils import list_context
label_desc: Use image node_id 3 for calling the RefFusedConvolutionGraph obj's underlying member method code with example usage: obj.get_grads(grad, need_grad_flags) and returns: np