code: def ref_sinc(x):
      if np.allclose(x, 0):
          return 1
      else:
          return np.sin(x) / 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_sinc(x) and returns: int, unknown