refactor(filetree): docs -> document, features -> feature, dev -> dev…

…elopment

hydro_roll_core/__init__.py

@@ -1 +1,2 @@
-from . import corelib
+from . import corelib
+

src/main.rs

@@ -0,0 +1,36 @@
+#![allow(unused)]
+fn main() {
+    use pyo3::prelude::*;
+
+    #[pymodule]
+    fn parent_module(py: Python<'_>, m: &PyModule) -> PyResult<()> {
+        register_child_module(py, m)?;
+        Ok(())
+    }
+
+    fn register_child_module(py: Python<'_>, parent_module: &PyModule) -> PyResult<()> {
+        let child_module = PyModule::new(py, "child_module")?;
+        child_module.add_function(wrap_pyfunction!(func, child_module)?)?;
+        parent_module.add_submodule(child_module)?;
+        Ok(())
+    }
+
+    #[pyfunction]
+    fn func() -> String {
+        "func".to_string()
+    }
+
+    Python::with_gil(|py| {
+        use pyo3::types::IntoPyDict;
+        use pyo3::wrap_pymodule;
+        let parent_module = wrap_pymodule!(parent_module)(py);
+        let ctx = [("parent_module", parent_module)].into_py_dict(py);
+
+        py.run(
+            "assert parent_module.child_module.func() == 'func'",
+            None,
+            Some(&ctx),
+        )
+        .unwrap();
+    })
+}