Fix ODE in plot example
//! result.write("example_data/test.csv");
//! }
//!
-//! fn test_fn(st: &mut State<f64>) {
+//! fn test_fn(st: &mut State<f64>, _: &NoEnv) {
//! let x = st.param;
//! let y = &st.value;
//! let dy = &mut st.deriv;
//! //plt.savefig();
//! }
//!
-//! fn test_fn(st: &mut State<f64>) {
+//! fn test_fn(st: &mut State<f64>, _: &NoEnv) {
//! let x = st.param;
//! let y = &st.value;
//! let dy = &mut st.deriv;
