code: def ref_gelu(x):
      return (
          x
          / 2
          * (
              1
              + np.tanh(
                  np.sqrt(2 / np.pi) * (x + 0.044715 * np.power(x, 3))
              )
          )
      )
  
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_gelu(x) and returns: unknown