Consider frozen and rely on underlying rust classes to manage mutability

Author: ntjohnson1

src/context.rs

@@ -296,7 +296,7 @@ impl PySQLOptions {
 /// `PySessionContext` is able to plan and execute DataFusion plans.
 /// It has a powerful optimizer, a physical planner for local execution, and a
 /// multi-threaded execution engine to perform the execution.
-#[pyclass(name = "SessionContext", module = "datafusion", subclass)]
+#[pyclass(frozen, name = "SessionContext", module = "datafusion", subclass)]
 #[derive(Clone)]
 pub struct PySessionContext {
     pub ctx: SessionContext,

src/substrait.rs

@@ -138,7 +138,7 @@ impl PySubstraitConsumer {
     /// Convert Substrait Plan to DataFusion DataFrame
     #[staticmethod]
     pub fn from_substrait_plan(
-        ctx: &mut PySessionContext,
+        ctx: &PySessionContext,
         plan: PyPlan,
         py: Python,
     ) -> PyDataFusionResult<PyLogicalPlan> {