Function approximate_jacobian_fd_into 

pub fn approximate_jacobian_fd_into<'a, T>(
    jacobian: impl Into<DMatrixViewMut<'a, T>>,
    f: impl FnMut(DVectorView<'_, T>, DVectorViewMut<'_, T>),
    x: impl Into<DVectorViewMut<'a, T>>,
    h: T,
)
where
    T: Real,

Approximates the Jacobian of the function $f: \mathbb{R}^n \rightarrow \mathbb{R}^m$ with finite differences.

Same as approximate_jacobian_fd, but stores the result in the provided output matrix.