from annotationlib import get_annotations, Format

class Demo:
    x: Sequence[undefined]

annos = get_annotations(Demo, format=Format.FORWARDREF)

x_anno = annos['x']

# Try to evaluate the reference, but just give a forwardref if it fails
x_repeat_anno = x_anno.evaluate(format=Format.FORWARDREF)

# The resulting reference no longer shares the globals namespace with the annotate function
print(f"{x_anno.__globals__ is Demo.__annotate__.__globals__ = }")  # True
print(f"{x_repeat_anno.__globals__ is Demo.__annotate__.__globals__ = }")  # False

# Define the previously undefined attributes
from collections.abc import Sequence
undefined = str

# This means evaluation fails in the second case
print(f"{x_anno.evaluate() = }")  # collections.abc.Sequence[str]
print(f"{x_repeat_anno.evaluate() = }")  # NameError

from annotationlib import get_annotations, Format
import typing

class Works:
    a: Sequence[undefined]
    b: unknowable

# Intentionally set up an annotation that will raise AttributeError on evaluation
class Fails:
    a: Sequence[undefined]
    b: typing.doesnotexist

a_works = get_annotations(Works, format=Format.FORWARDREF)['a']
a_fails = get_annotations(Fails, format=Format.FORWARDREF)['a']

# Realise the references
from collections.abc import Sequence
undefined = str

print(f"{a_works.evaluate() = }")  # collections.abc.Sequence[str]
print(f"{a_fails.evaluate() = }")  # NameError