code: def test_empty_input(self):
      with pytest.raises(ValueError, match="Invalid number of CZT"):
          signal.czt([])
      with pytest.raises(ValueError, match="Invalid number of CZT"):
          signal.zoom_fft([], 0.5)
  
imports: from math import pi
  import pytest
  import cupy
  import numpy
  from cupy import testing
  from cupy.testing import assert_allclose
  import cupyx.scipy.fft
  import cupyx.scipy.signal
label_desc: Use image node_id 4 for calling the TestErrors obj's underlying member method code with example usage: obj.test_empty_input() without return types