code: def sinegauss_PSD(f, t0, f0, a):
      """PSD of the sine-gaussian wavelet
      PSD(f) = |H(f)|^2 + |H(-f)|^2
      """
      Pf = np.pi / a * np.exp(-2 * np.pi**2 * (f - f0) ** 2 / a)
      Pmf = np.pi / a * np.exp(-2 * np.pi**2 * (-f - f0) ** 2 / a)
      return Pf + Pmf
  
file_path: astroML/astroML/tests/test_fourier.py
imports: import pytest
  import numpy
  from numpy.testing import assert_allclose
  from astroML.fourier import FT_continuous, IFT_continuous, PSD_continuous, sinegauss, sinegauss_FT
label_desc: Use image node_id 4 for calling a global function with example usage: sinegauss_PSD(f, t0, f0, a) and returns: unknown