'Gets the gradients with respect to the inputs of the module.
Parameters
merge_multi_context : bool
Defaults to ``True``. In the case when data-parallelism is used, the outputs
will be collected from multiple devices. A ``True`` value indicate that we
should merge the collected results so that they look like from a single
executor.
Returns
list of NDArrays or list of list of NDArrays
If `merge_multi_context` is ``True``, it is like ``[grad1, grad2]``. Otherwise, it
is like ``[[grad1_dev1, grad1_dev2], [grad2_dev1, grad2_dev2]]``. All the output
elements are `NDArray`.'

def get_input_grads(self, merge_multi_context=True):

    assert (self.binded and self.params_initialized and self.inputs_need_grad)
    return self._curr_module.get_input_grads(merge_multi_context=merge_multi_context)
