Describe the bug
PlainSerializer when_used literal giving PyCharm inspection false positive of: "unresolved reference 'json'".
This doesn't reproduce in a scratch file for some reason. This is a weird bug and may be upstream.

Is there anything I can do to help determine if this is a plugin issue or upstream issue?

To Reproduce

from datetime import datetime
from typing import Annotated, TypeAlias
from pydantic import PlainSerializer

def datetime_to_epoch_ms(timestamp: datetime) -> int:
    if timestamp.tzinfo is None:
        timestamp = timestamp.astimezone()
    return int(timestamp.timestamp() * 1000)

Timestamp: TypeAlias = Annotated[
    datetime,
    PlainSerializer(
        # when_used="json" is giving PyCharm inspection false positive of: "unresolved reference 'json'"
        lambda timestamp: 0 if timestamp is None else datetime_to_epoch_ms(timestamp),
        return_type=int,
        when_used="json",
    ),
]

Expected behavior
when_used value should be recognized as acceptable literal as in the scratch file.

Screenshots

Environments (please complete the following information):

• IDE: PyCharm Pro 2023.3
• OS: Fedora 39 Workstation
• Python 3.11.6
• Pydantic Version 2.5.2
• Pydantic Plugin 0.4.10
• Ruff Version 0.1.8
• Ruff LSP Version 0.0.48
• Ruff Plugin 0.0.28

Additional context
I already tried Invalidate Caches feature (all boxes checked) and it didn't help.