- Validate argument types before resolving fields: list arguments now
produce helpful errors when passed objects instead of lists
- Add isOneOf field to type introspection for INPUT_OBJECT types
(GraphQL spec compliance)

Bump version to 2.0.1

- Add named_type_name function to get base type without List/NonNull wrappers
- Fix fragment spread type condition matching on NonNull/List wrapped types
- Fix inline fragment type condition matching with wrapped types
- Fix __typename to return concrete type name without modifiers

Add GraphQL spec-compliant default value support for variable definitions.

Features:
- Parse `$name: Type = defaultValue` syntax in queries, mutations, and subscriptions
- Apply default values during execution when variables are not provided
- Provided variables override default values

BREAKING CHANGE: Variable type now has 3 fields instead of 2.
Update pattern matches from `Variable(name, type_)` to `Variable(name, type_, default_value)`.

Add parse_type_reference function to handle GraphQL list type syntax
in variable definitions. Supports all list type variants:
- [Type] - nullable list of nullable items
- [Type!] - nullable list of non-null items
- [Type]! - non-null list of nullable items
- [Type!]! - non-null list of non-null items

Includes tests for all list type combinations.