bug: fix chirpradon3d pyfftw import

Remove any direct access to pyfftw and instead use
pyfftw_message to check if the library is installed
and correctly imported.

pylops/signalprocessing/chirpradon3d.py

@@ -101,23 +101,23 @@ def __init__(
 
     @reshaped
     def _matvec(self, x: NDArray) -> NDArray:
-        if self.engine == "fftw" and pyfftw is not None:
+        if self.engine == "fftw" and pyfftw_message is None:
             return _chirp_radon_3d_fftw(
                 x, self.dt, self.dy, self.dx, self.pmax, mode="f", **self.kwargs_fftw
             )
         return _chirp_radon_3d(x, self.dt, self.dy, self.dx, self.pmax, mode="f")
 
     @reshaped
     def _rmatvec(self, x: NDArray) -> NDArray:
-        if self.engine == "fftw" and pyfftw is not None:
+        if self.engine == "fftw" and pyfftw_message is None:
             return _chirp_radon_3d_fftw(
                 x, self.dt, self.dy, self.dx, self.pmax, mode="a", **self.kwargs_fftw
             )
         return _chirp_radon_3d(x, self.dt, self.dy, self.dx, self.pmax, mode="a")
 
     def inverse(self, x: NDArray) -> NDArray:
         x = x.reshape(self.dimsd)
-        if self.engine == "fftw" and pyfftw is not None:
+        if self.engine == "fftw" and pyfftw_message is None:
             y = _chirp_radon_3d_fftw(
                 x, self.dt, self.dy, self.dx, self.pmax, mode="i", **self.kwargs_fftw
             )