Fix module name in getting started

guide/src/getting_started.md

@@ -153,7 +153,7 @@ fn sum_as_string(a: usize, b: usize) -> PyResult<String> {
 /// the `lib.name` setting in the `Cargo.toml`, else Python will not be able to
 /// import the module.
 #[pymodule]
-fn string_sum(_py: Python<'_>, m: &PyModule) -> PyResult<()> {
+fn pyo3_example(_py: Python<'_>, m: &PyModule) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(sum_as_string, m)?)?;
     Ok(())
 }