code: def ref_ifft(x, signal_ndim, normalized):
      from nbla_test_utils import (
          convert_to_float2_array,
          convert_to_complex_array,
      )
  
      x_data_complex = convert_to_complex_array(x)
      batch_dims = x_data_complex.shape[
          0 : len(x_data_complex.shape) - signal_ndim
      ]
      ref_data_complex = np.fft.ifftn(
          x_data_complex,
          axes=np.arange(signal_ndim) + len(batch_dims),
          norm="ortho" if normalized else None,
      )
  
      ref_data_float2 = convert_to_float2_array(
          ref_data_complex
      ).astype(np.float32)
      return ref_data_float2
  
file_path: nnabla/python/test/function/test_ifft.py
imports: import pytest
  import numpy
  import sys
  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_ifft(x, signal_ndim, normalized) and returns: ref_data_float2