Function dasp::slice::add_in_place_with_amp_per_channel

pub fn add_in_place_with_amp_per_channel<FA, FB, A>(
    a: &mut [FA], 
    b: &[FB], 
    amp_per_channel: A
) where
    A: Frame<Sample = <<FB as Frame>::Sample as Sample>::Float, NumChannels = <FB as Frame>::NumChannels>,
    FA: Frame,
    FB: Frame<Sample = <<FA as Frame>::Sample as Sample>::Signed, NumChannels = <FA as Frame>::NumChannels>, 

Scale the amplitude of each frame in b by amp_per_channel before summing it onto a.