Fix NotImplementedError

✅ Solution

NotImplementedError in FastAPI often arises when a custom type lacks explicit handling for JSON serialization or schema generation, especially when `arbitrary_types_allowed=True`. To fix this, implement `__get_validators__` and `json_encoders` within your custom type to define how it is serialized and represented in the OpenAPI schema, or use a suitable pydantic field type for serialization. Ensure that pydantic can properly understand and serialize the custom type when generating the OpenAPI schema.