code: def ref_huber_loss(x0, x1, delta):
      grad = x0 - x1
      q = np.minimum(np.abs(grad), delta)
      l = np.abs(grad) - q
      return q**2 + 2 * delta * l
  
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_huber_loss(x0, x1, delta) and returns: unknown