message: FEAT: Slice to node/edge bound when serializing StableGraph
  We don't want to insert extra holes past the last valid index for these
  graphs, those positions don't matter.
diff: @@ -15,6 +15,7 @@ use util::rev;
  use serde_utils::MappedSequenceVisitor;
  use serde_utils::CollectSeqWithLength;
  use serde_utils::{IntoSerializable, FromDeserialized};
  +use visit::NodeIndexable;
  use super::super::serialization::{EdgeProperty, invalid_length_err, invalid_node_err};
  @@ -131,10 +132,12 @@ impl<'a, N, E, Ty, Ix> IntoSerializable for &'a StableGraph<N, E, Ty, Ix>
  {
  type Output = SerStableGraph<'a, N, E, Ix>;
  fn into_serializable(self) -> Self::Output {
  + let nodes = &self.raw_nodes()[..self.node_bound()];
  + let edges = &self.raw_edges()[..self.edge_bound()];
  SerStableGraph {
  - nodes: self.raw_nodes(),
  - node_holes: self.raw_nodes(),
  - edges: self.raw_edges(),
  + nodes: nodes,
  + node_holes: nodes,
  + edges: edges,
  edge_property: EdgeProperty::from(PhantomData::<Ty>),
  }
  }
  