Python: how to safely initialize a dataclass based on a dict with unexpected keys?

Question

I'd like to initialize A from a dict which can contain unexpected keys. I'd like to initialize with the given, known keys and ignore the rest.

from dataclasses import dataclass

@dataclass
class A:
    a: str
    b: int

a1 = A(**{'a': 'Foo', 'b': 123})  # works
a2 = A(**{'a': 'Foo', 'b': 123, 'c': 'unexpected'})  # raises TypeError

Is there a Python feature that I'm missing or do I have to filter the dict upfront?