Snapshot

## Description Add an api to get last frame ## Related Issue <!--- This project only accepts pull requests related to open issues --> <!--- If suggesting a new feature or change, please discuss it in an issue first --> <!--- If fixing a bug, there should be an issue describing it with steps to reproduce --> <!--- Please link to the issue here: --> ## Motivation and Context <!--- Why is this change required? What problem does it solve? --> ## Types of changes <!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: --> - [ ] Docs change / refactoring / dependency upgrade - [ ] Bug fix (non-breaking change which fixes an issue) - [x ] New feature (non-breaking change which adds functionality) - [ ] Breaking change (fix or feature that would cause existing functionality to change)