ef forward(self, x: Tensor) -&gt; Tensor:
        &#34;&#34;&#34;STFT forward path
        Args:
            x (Tensor): audio waveform of
                shape (nb_samples, nb_channels, nb_timesteps)
        Returns:
            STFT (Tensor): complex stft of
                shape (nb_samples, nb_channels, nb_bins, nb_frames, complex=2)
                last axis is stacked real and imaginary
        &#34;&#34;&#34;

        shape = x.size()
        nb_samples, nb_channels, nb_timesteps = shape

        # p