Function istft 

pub fn istft(
    stft_matrix: Tensor<4>,
    window: Option<Tensor<1>>,
    length: Option<usize>,
    options: StftOptions,
) -> Tensor<2>

Computes the inverse Short-Time Fourier Transform (ISTFT).

Reconstructs a time-domain signal from its STFT representation using overlap-add.

Arguments

• stft_matrix - Complex STFT tensor of shape [batch, n_frames, n_freqs, 2].
• window - Window tensor used in the forward STFT. Defaults to rectangular.
• length - Optional output signal length. If None, the length is inferred.
• options - STFT configuration (must match the forward STFT).

Returns

A real-valued tensor of shape [batch, signal_length].