def test_serialize_sequence_value_with_optional_list():
    """Test that serialize_sequence_value handles optional lists correctly."""
    from fastapi._compat import v2

    field_info = FieldInfo(annotation=Union[list[str], None])
    field = v2.ModelField(name="items", field_info=field_info)
    result = v2.serialize_sequence_value(field=field, value=["a", "b", "c"])
    assert result == ["a", "b", "c"]

from .v2 import is_scalar_field as is_scalar_field
from .v2 import is_scalar_sequence_field as is_scalar_sequence_field
from .v2 import is_sequence_field as is_sequence_field
from .v2 import serialize_sequence_value as serialize_sequence_value
from .v2 import (
    with_info_plain_validator_function as with_info_plain_validator_function,

    is_scalar_sequence_field,
    is_sequence_field,
    is_uploadfile_or_nonable_uploadfile_annotation,
    is_uploadfile_sequence_annotation,
    lenient_issubclass,
    sequence_types,
    serialize_sequence_value,
    value_is_sequence,
)
from fastapi.background import BackgroundTasks
from fastapi.concurrency import (
    asynccontextmanager,
    contextmanager_in_threadpool,
)

    new_field_info = copy(field_info)
    new_field_info.metadata = merged_field_info.metadata
    new_field_info.annotation = merged_field_info.annotation
    return new_field_info


def serialize_sequence_value(*, field: ModelField, value: Any) -> Sequence[Any]:
    origin_type = get_origin(field.field_info.annotation) or field.field_info.annotation
    if origin_type is Union or origin_type is UnionType:  # Handle optional sequences