Vellum-ai

- Fixes a bug on `vellum workflows push` for Workflows that utilize `LazyReference`s
- Properly genererates code for optional input and output variables using `typing.Optional`
- Supports serialization for both State variables and State references
- Adds better error handling for empty input on jinja templating

- [BREAKING] Renames our `UNDEF` singleton to `undefined` for future consistency with TypeScript SDKs.
- Fixes use of `cancel_signal` for Workflow executions that don't need to cancel.
- Node classes now auto-inherit from it's inherited node class' Outputs classes avoiding the need to manually inherit.
- Support 'contains' and 'does not contains' expressions now support WorkflowError as a valid operand.
- Fixes hanging experienced by map nodes when given an empty `items` list.
- Workflow classes now auto-inherit from it's inherited Workflow class' Outputs classes avoiding the need to manually inherit.
- Supports string indexing in inline code execution nodes for attribute access
- Avoids the code generation of authorization type if not provided from API Node
- Fixes a bug during sandbox code generation that would fail if there was a null string input present
- Fixes a bug during inline code execution nodes for NUMBER output types

- Code Execution Node Number Outputs now support both int and float values
- Fixes a bug surrounding the code generation of the `deployment` attribute on Prompt Deployment Nodes
- HTTP errors during Prompt Deployment nodes now properly surface
- Fixes a bug surrounding a Conditional node's handling of undefined values
- Properly surface user errors on Port conditions
- Supports pushing new workflow modules to Vellum that are not previously configured in lockfile
- Fixes a bug where null values from API Nodes were not properly handled

- Fixes a graph generation case with multiple branches into a single node
- Fixes a bug where subworkflows were generating the same outputs as the parent workflow

- Fixes a bug where prompt function definitions were not being pushed for Prompt Nodes

- Introduces support for using LazyReference with strings, to get around circular reference issues
- Also supports code generation and serialization of Lazy References of Nodes
- Fixes a bug where subworkflow and map nodes directories were not being generated
- Fixes a bug where null Chat History values were failing `vellum workflows pull`
- Outputs of Generic Nodes are now properly code generated.
- Fixes a bug preventing Code Generation of Workflows if there was corrupted edge data in the Workflow.
- Fixes a bug where prompt function definitions were not being generated for Prompt Nodes