Function save_nifti_4d_gz 

pub fn save_nifti_4d_gz(
    volumes: &[&[f64]],
    dims: (usize, usize, usize),
    voxel_size: (f64, f64, f64),
    affine: &[f64; 16],
) -> Result<Vec<u8>, String>

save_nifti_4d, gzipped (.nii.gz).