Add test for nested Optional behavior

Author: BHUVANSH855

conformance/tests/specialtypes_optional_nested.py

@@ -0,0 +1,16 @@
+"""
+Tests for behavior of nested Optional types collapsing.
+
+Optional[Optional[T]] should behave as Optional[T].
+"""
+
+from typing import Optional, assert_type
+
+
+def test_nested_optional(x: Optional[Optional[int]]) -> None:
+    # Should behave like Optional[int]
+    assert_type(x, Optional[int])
+
+
+def test_nested_optional_error(x: Optional[Optional[int]]) -> int:
+    return x  # E