code: def forward_backward_all(*vv):
      y = F.sink(*vv)
      y.forward()
      y.backward()
  
imports: import pytest
  import numpy
  import nnabla
  import nnabla.functions
  import nnabla.parametric_functions
  import nnabla.initializer
  from nnabla.testing import assert_allclose
  from nbla_test_utils import list_context
label_desc: Use image node_id 6 for calling a global function with example usage: forward_backward_all() without return types