#3396 Generalize custom type detection in nested Pydantic models Pull request opened by AdilFayyaz ## Tracking issue Duplicated from: flyteorg/flyte-sdk#664 ## Why are the changes needed? Ensure flytekit is up to date with flytesdk ## What changes were proposed in this pull request? • When guess_python_type reconstructs a Python type from a Flyte LiteralType (JSON schema), nested custom types with registered TypeTransformers were being rebuilt as generic dataclasses instead of being recognized as their original types. This is because the schema reconstruction code never consulted TypeEngine._REGISTRY for registered types when resolving $ref entries or inline nested objects. • Added schema_match() method to TypeTransformer that auto-matches for BaseModel subclasses by comparing JSON schema fingerprints (title, type, required fields). No user override needed — registering a transformer for a BaseModel subclass is sufficient. • Added _match_registered_type_from_schema() helper that iterates all registered transformers to find a match. • Replaced the fallback-to-generic-dataclass paths in generate_attribute_list_from_dataclass_json_mixin, _handle_json_schema_property, and _get_element_type with the generalized helper, so any registered custom type is recognized before a synthetic dataclass is created. ## How was this patch tested? pytest tests/flytekit/unit/core/test_custom_type_in_nested_pydantic.py — 7 new tests covering _match_registered_type_from_schema (match, no match), guess_python_type structure verification (direct, List, Dict, nested List), and default schema_match behavior. Note: File/Dir schema match tests and the mixed-type model test from v2 are not included because FlyteFile/FlyteDirectory are not BaseModel subclasses in v1 and therefore do not benefit from the auto-match logic. ### Setup process ### Screenshots ## Check all the applicable boxes • I updated the documentation accordingly. • All new and existing tests passed. • All commits are signed-off. ## Related PRs ## Docs link flyteorg/flytekit