code: def test_minimal_length_signal(m_num):
      """Verify that the shortest allowed signal works."""
      SFT = ShortTimeFFT(np.ones(m_num), m_num // 2, fs=1)
      n = math.ceil(m_num / 2)
      x = np.ones(n)
      Sx = SFT.stft(x)
      x1 = SFT.istft(Sx, k1=n)
      assert_allclose(
          x1,
          x,
          err_msg=f"Roundtrip minimal length signal ({n=})"
          + f" for {m_num} sample window failed!",
      )
      with pytest.raises(
          ValueError, match=rf"len\(x\)={n-1} must be >= ceil.*"
      ):
          SFT.stft(x[:-1])
      with pytest.raises(
          ValueError,
          match=rf"S.shape\[t_axis\]={Sx.shape[1]-1}"
          f" needs to have at least {Sx.shape[1]} slices",
      ):
          SFT.istft(Sx[:, :-1], k1=n)
  
imports: import math
  from itertools import product
  from typing import cast, get_args, Literal
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_equal
  from scipy.fft import fftshift
  from scipy.stats import norm
  from scipy.signal import get_window, welch, stft, istft, spectrogram
  from scipy.signal._short_time_fft import FFT_MODE_TYPE, _calc_dual_canonical_window, ShortTimeFFT, PAD_TYPE
  from scipy.signal.windows import gaussian
label_desc: Use image node_id 22 for calling a global function with example usage: test_minimal_length_signal(m_num) without return types