Worked on the pytorch/tensordict repository to enhance the stability and type safety of key iteration within TensorDict. Focused on Python development and bug fixing, the work involved refactoring the _iter_helper function to properly handle tuple prefixes and adding a guard assertion to ensure _param_td is not None in TensorDictParams. Additionally, the logic for creating shape memmap files was refined to prevent edge-case errors. These targeted improvements, leveraging Python and type hinting, reduced runtime errors in key-iteration paths and improved code maintainability, directly benefiting downstream users by making the iteration process more robust and less prone to subtle bugs.