Coordinate cannot be used as optional field

[lgln-kmi]

Following code:

from pydantic import BaseModel
from pydantic_extra_types.coordinate import Coordinate
from typing import Optional

class A( BaseModel ):
  c: Optional[ Coordinate ] = None

a = A()

cannot be run

  File "pydantic_coordinate.py", line 10, in <module>
    a = A()
        ^^^
  File "/usr/local/lib/python3.11/site-packages/pydantic/main.py", line 165, in __init__
    __pydantic_self__.__pydantic_validator__.validate_python(data, self_instance=__pydantic_self__)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/pydantic/_internal/_mock_val_ser.py", line 47, in __getattr__
    raise PydanticUserError(self._error_message, code=self._code)
pydantic.errors.PydanticUserError: `A` is not fully defined; you should define `Latitude`, then call `A.model_rebuild()`.

Selected Assignee: @Kludex