[Python] 'ABCMeta' object is not subscriptable when trying to annotate a hash variable

The following dataclass:

from abc import ABC
from collections.abc import Mapping
from dataclasses import dataclass, field

@dataclass(eq=True, order=True, frozen=True)
class Expression(Node, ABC):
def node(self):
raise NotImplementedError


is used as a base class for:

@dataclass(eq=True, frozen=True)
class HashLiteral(Expression):
pairs: Mapping[Expression, Expression]
...


Node is defined as:

@dataclass(eq=True, frozen=True)
class Node:
def __str__(self) -> str:
raise NotImplementedError


When trying to use the HashLiteral class I get the error:

pairs: Mapping[Expression, Expression]
TypeError: 'ABCMeta' object is not subscriptable


What is wrong with my annotation of pairs above?

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