code: def ref_linspace_half(start, stop, num):
      return np.linspace(start, stop, num).astype(np.float16)
  
file_path: nnabla/python/test/function/test_linspace.py
imports: import pytest
  import numpy
  import nnabla.functions
  from nbla_test_utils import list_context, function_tester, half_test, force_tuple
  from nnabla.testing import assert_allclose
  import nnabla
  import nnabla.ext_utils
label_desc: Use image node_id 3 for calling a global function with example usage: ref_linspace_half(start, stop, num) and returns: np