code: def ref_mish(x):
      return x * np.tanh(np.log(np.exp(x, dtype=x.dtype) + 1))
  
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_mish(x) and returns: unknown