- fix some pickling issues

src/py.rs

@@ -1,4 +1,3 @@
-use anyhow::anyhow;
 use crate::Ome;
 use crate::ome::{
     Convert, UnitsElectricPotential, UnitsFrequency, UnitsLength, UnitsPower,
@@ -6,39 +5,7 @@ use crate::ome::{
 };
 use pyo3::exceptions::PyValueError;
 use pyo3::prelude::*;
-use pyo3::IntoPyObjectExt;
 
-/// helper class to be used for unpickling
-#[pyclass(module = "ome_metadata.ome_metadata_rs")]
-struct Constructor;
-
-#[pymethods]
-impl Constructor {
-    #[new]
-    fn new() -> Self {
-        Self
-    }
-
-    fn __getstate__(&self) -> (u8,) {
-        (0,)
-    }
-
-    fn __setstate__(&self, _state: (u8,)) {}
-
-    #[staticmethod]
-    fn __call__(py: Python, class: String, variant: String) -> PyResult<Bound<PyAny>> {
-        match class.as_str() {
-            "ElectricPotential" => ElectricPotential::new(&variant)?.into_bound_py_any(py),
-            "Frequency" => Frequency::new(&variant)?.into_bound_py_any(py),
-            "Length" => Length::new(&variant)?.into_bound_py_any(py),
-            "Power" => Power::new(&variant)?.into_bound_py_any(py),
-            "Pressure" => Pressure::new(&variant)?.into_bound_py_any(py),
-            "Temperature" => Temperature::new(&variant)?.into_bound_py_any(py),
-            "Time" => Time::new(&variant)?.into_bound_py_any(py),
-            _ => Err(anyhow!("cannot parse class {}", class).into())
-        }
-    }
-}
 
 macro_rules! impl_enum_into_py_object {
     ($($s:ident: $t:ty $(,)?)*) => {
@@ -79,9 +46,9 @@ macro_rules! impl_enum_into_py_object {
                 fn __str__(&self) -> String {
                     format!("{:?}", self.inner)
                 }
-
-                fn __reduce__(&self) -> PyResult<(Constructor, (String, String))> {
-                    Ok((Constructor, (stringify!($s).to_string(), format!("{:?}", self.inner))))
+                
+                fn __getnewargs__(&self) -> (String,) {
+                    (format!("{:?}", self.inner),)
                 }
             }
 
@@ -110,7 +77,6 @@ impl_enum_into_py_object! {
 #[pymodule]
 #[pyo3(name = "ome_metadata_rs")]
 fn ome_metadata_rs(m: &Bound<'_, PyModule>) -> PyResult<()> {
-    m.add_class::<Constructor>()?;
     m.add_class::<ElectricPotential>()?;
     m.add_class::<Frequency>()?;
     m.add_class::<Length>()?;