code: def ref_elu(x, alpha):
      return np.maximum(x, 0) + alpha * (np.exp(np.minimum(x, 0)) - 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_elu(x, alpha) and returns: unknown