code: def ref_softmax(x, axis):
      x = x - x.max(axis, keepdims=True)
      x = np.exp(x) / np.exp(x).sum(axis, keepdims=True)
      return x
  
imports: import pytest
  import numpy
  import nnabla.functions
  from nbla_test_utils import list_context
label_desc: Use image node_id 1 for calling a global function with example usage: ref_softmax(x, axis) and returns: x