keras/src/backend/tensorflow/math.py/rfft
def rfft(x, fft_length=None):
    if fft_length is not None:
        fft_length = [fft_length]
    complex_output = tf.signal.rfft(x, fft_length=fft_length)
    return tf.math.real(complex_output), tf.math.imag(complex_output)