code: def sum_for_arithmetics(dx, x):
      # F.{add2, sub2, mul2, div2} includes Broadcast internally (C++-level),
      # so we have to do F.sum explicitly
      axes = [a for a in range(len(x.shape)) if x.shape[a] == 1]
      dx = F.sum(dx, axes, keepdims=True)
      return dx
  
file_path: nnabla/python/src/nnabla/backward_function/utils.py
imports: import nnabla.functions
label_desc: Use image node_id 6 for calling a global function with example usage: sum_for_arithmetics(dx, x) and returns: dx