message: NoneType implement serde Serializable
diff: @@ -20,6 +20,7 @@ use std::hash::Hasher;
  use derive_more::Display;
  use gazebo::{any::AnyLifetime, prelude::*};
  +use serde::{Serialize, Serializer};
  use crate::{
  collections::{StarlarkHashValue, StarlarkHasher},
  @@ -84,6 +85,15 @@ impl<'v> AllocValue<'v> for NoneType {
  }
  }
  +impl Serialize for NoneType {
  + fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
  + where
  + S: Serializer,
  + {
  + serializer.serialize_none()
  + }
  +}
  +
  impl AllocFrozenValue for NoneType {
  fn alloc_frozen_value(self, _heap: &FrozenHeap) -> FrozenValue {
  FrozenValue::new_none()
  