dataclass signature pop-up shows "The most base type"

[roblevy]

I'm using coc-python for Python IDE-like features.

If I define a dataclass I would expect the signature pop-up to show me which fields an instance of this class expects.

Instead I get:

MyClass()
------------------
The most base type

Here is a screenshot which shows the coc-python output:

By contrast, a normal class with an __init__ method shows the expected signature:

---

Minimum working example

from dataclasses import dataclass

@dataclass
class Shape:
    radius: int
    sides: int